Power management in single circuit hvac systems and in multiple circuit hvac systems

ABSTRACT

A thermostat includes a plurality of HVAC (heating, ventilation, and air conditioning) wire connectors for receiving a plurality of HVAC control wires corresponding to an HVAC system. The thermostat also includes a thermostat processing and control circuit operative to at least partially control the operation of the HVAC system and a powering circuit coupled to the HVAC wire connectors and configured to provide an electrical load power to the thermostat processing and control circuit. The thermostat includes circuitry and methods for maximizing efficiency of energy harvested from the HVAC system connected to the thermostat, and depending on which system is connected to the thermostat, different power schemes can be implemented in order to obtain power from the HVAC system.

CROSS-REFERENCES TO RELATED APPLICATIONS

This patent application is a continuation-in-part of each of thefollowing commonly-assigned applications: U.S. patent application Ser.No. 13/467,025 (Attorney Docket No. NES0177-US), filed May 8, 2012; PCTApplication No. PCT/US12/00007 (Attorney Docket No. NES0190-PCT), filedJan. 3, 2012; U.S. patent application Ser. No. 13/267,877 (AttorneyDocket No. NES0100-US), filed Oct. 6, 2011; U.S. patent application Ser.No. 13/034,674 (Attorney Docket No. NES0006-US), filed Feb. 24, 2011;and U.S. patent application Ser. No. 13/034,678 (Attorney Docket No.NES0007-US), filed Feb. 24, 2011. Each of U.S. patent application Ser.Nos. 13/267,877, 13/034,674, and 13/034,678, supra, claims the benefitof each of U.S. Provisional Patent Application Nos. 61/415,771 (AttorneyDocket No. NES037-PROV), filed Nov. 19, 2010, and 61/429,093 (AttorneyDocket No. NES037A-PROV), filed Dec. 31, 2010. Each of U.S. patentapplication Ser. No. 13/467,025 and PCT Application No. PCT/US12/00007,supra, claims the benefit of U.S. Provisional Patent Application No.61/627,996 (Attorney Docket No. NES0101-PROV), filed Oct. 21, 2011.

Each of the above-referenced patent applications is incorporated hereinby reference in its entirety for all purposes.

TECHNICAL FIELD

This patent specification relates to systems and methods for themonitoring and control of energy-consuming systems or otherresource-consuming systems. More particularly, this patent specificationrelates to control units that govern the operation of energy-consumingsystems, household devices, or other resource-consuming systems,including systems and methods for providing electrical power forthermostats that govern the operation of heating, ventilation, and airconditioning (HVAC) systems.

BACKGROUND

Substantial effort has been put forth on the development of new and moresustainable energy supplies, as well as efforts to increase energyefficiency of existing energy consumption systems. An example of anenergy consumption system is the heating and cooling system of anenclosure such as a home or building. According to a report from theUnited States Department of Energy, heating and cooling can account for56% of the energy use in a typical home, making it a significant energyexpense. Heating and cooling systems can realize greater efficiency byimproving physical aspects of the system (e.g., higher efficiencyfurnace) and enclosure (e.g., more or better insulation). Substantialincreases in energy efficiency can also be achieved through enhancedthermostat control of the heating and cooling system.

Thermostats of all types have been used to control heating and coolingsystems. For example, older generation thermostats were strictlymechanical devices that used a bimetallic strip to sense temperature,and controlled an HVAC system based on the sensed temperature. Themechanical thermostats required neither electronics nor power tooperate, because the strip itself would activate or deactivate circuitrywithin the HVAC system. This changed, however, when thermostats evolvedto include electronics. Electronic thermostats, though requiring a powersource in order to operate, offered more advanced HVAC control ascompared to their mechanical counterparts. For example, an electronicthermostat can be programmed to have multiple temperature set points ina given day. As another example, advanced microprocessor controlled“intelligent” thermostats may have further enhanced HVAC system controlcapabilities. These thermostats may also be capable of connecting tocomputer networks, including both local area networks (or other“private” networks) and wide area networks such as the Internet (orother “public” networks), in order to obtain current and forecastedoutside weather data, cooperate in so-called demand-response programs(e.g., automatic conformance with power alerts that may be issued byutility companies during periods of extreme weather), enable users tohave remote access and/or control thereof through theirnetwork-connected device (e.g., smartphone, tablet computer, PC-basedweb browser), and other advanced functionalities that may requirenetwork connectivity.

Increases in functionality for electronic thermostats are oftenaccompanied by increased demands for power. Accordingly, what are neededare electronic thermostats that can maximize its own power consumptionefficiency depending on the HVAC system it is controlling.

SUMMARY

This patent specification relates to systems and methods for themonitoring and control of energy-consuming systems or otherresource-consuming systems. More particularly, this patent specificationrelates to control units that govern the operation of energy-consumingsystems, household devices, or other resource-consuming systems,including systems and methods for providing electrical power forthermostats that govern the operation of heating, ventilation, and airconditioning (HVAC) systems. Even more particularly, this patentspecification relates to circuitry and methods for maximizing efficiencyof energy harvested from the HVAC system connected to the thermostat.HVAC systems exist in all types of different configurations, anddepending on which system is connected to the thermostat, differentpower schemes can be implemented in order to obtain power from the HVACsystem.

Each HVAC system can fall into one of three general HVAC wiring schemes.These schemes include a single circuit system having no common wire, amultiple circuit system having no common wire, and a common wire system.A single circuit system with no common wire includes wiringconfigurations in which only one call relay wire (e.g., W, Y, G, O/B, orAUX) and its associated return relay power wire (e.g., Rh or Rc) areconnected to the thermostat, and no “C” power wire (e.g., common wire)is connected to the thermostat. The “single” designation implies thatonly one call can be made by the thermostat for this particular HVACwiring scheme. A multiple circuit system with no common wire includeswiring configurations in which at least two different call relay wires(e.g., W, Y, G, O/B, or AUX) are connected to the thermostat, but no “C”power wire is connected to the thermostat. The “multiple” designationimplies that at least two different calls can be made by the thermostat.A common wire system includes a wiring configuration in which a “C”common power wire and any combination of call relay wires and relaypower wires are connected to the thermostat.

Depending on which HVAC wiring scheme is connected to the thermostat, apower scheme specifically curtailed to that wiring scheme can beimplemented. The power schemes can use different methods for drawingpower from the HVAC system. These methods include active power stealing,inactive power stealing, and drawing dedicated “C” power. As usedherein, “active power stealing” refers to the power stealing that isperformed during periods in which there is an active call in place basedon the lead from which power is being stolen. As used herein, “inactivepower stealing” refers to the power stealing that is performed duringperiods in which there is no active call in place based on the lead fromwhich power is being stolen. Drawing dedicated “C” power does notconstitute “power stealing” per se because there is no power being“stolen” from a wire that leads to an HVAC call relay coil (or to theelectronic equivalent of an HVAC call relay coil for some newer HVACsystems). For the case in which the “C” wire is present, there is noneed to worry about accidentally tripping (for inactive power stealing)or untripping (for active power stealing) an HVAC call relay, andtherefore relatively large amounts of power can be assumed to beavailable to be drawn from the HVAC system.

Inactive power stealing is generally more power efficient for extractingpower from the HVAC system than active power stealing. Accordingly,various embodiments discussed herein provide circuits and techniques forutilizing this power efficiency advantage when no C wire is connected tothe thermostat. In one embodiment, a thermostat can include a pluralityof HVAC wire connectors operative to receive a plurality of HVAC wirescorresponding to an HVAC system, control circuitry operative to at leastpartially control the operation of the HVAC system, and power wireselection circuitry connected to the HVAC wire connectors and to thecontrol circuitry. The power wire selection circuitry can be operativeto select which wire connector is electrically coupled to a power node.The thermostat can also include powering circuitry operative to receivepower from the power wire selection circuitry via the power node andreceive control signals from the control circuitry. The controlcircuitry can be further operative to determine an HVAC wiring schemebased on which wire connectors have received HVAC wires, cause thepowering circuitry to operate according to a selected one of a pluralityof power schemes based on the determined HVAC wiring scheme, andinstruct the power wire selection circuitry to selectively couple apredetermined one of the wire connectors to the power node based on thedetermined HVAC wiring scheme and the selected power scheme.

In another embodiment, a method for controlling an HVAC system can beimplemented in a thermostat. The method can determine which one of aplurality of different HVAC wiring schemes is connected to thethermostat, the plurality of different HVAC wiring schemes including asingle circuit system having no common wire, a multiple circuit systemhaving no common wire, and a common wire system. The method can furtherimplement a power scheme based on the determined HVAC wiring scheme. Ifthe determined HVAC wiring scheme is the single circuit system, theimplemented power scheme uses active and inactive power stealing on thesingle circuit system. If the determined HVAC wiring scheme is themultiple circuit system, the implemented power scheme only uses inactivepower stealing on a non-enabled circuit within the multiple circuitsystem. If the determined HVAC wiring scheme is the common wire system,the implemented power scheme uses neither active power stealing norinactive power stealing.

In another embodiment, a thermostat can include a plurality of wiringconnectors operative to connect to a plurality of HVAC wires andinsertion sensing circuitry operative to provide insertion sensingsignals indicative of which wiring connectors have an HVAC wireconnected thereto. The thermostat can also include power wire selectioncircuitry, which can include an output node, a control node, and atleast two input nodes. Each input node can be electrically coupled to adifferent one of at least two wiring connectors, and the power wireselection circuitry can be operative to selectively couple any inputnode to the output node based on a signal received at the control node.A microcontroller can be included with the thermostat and can beoperative to receive the insertion sensing signals and process HVAC callsignals, the HVAC call signals including at least two different types ofcalls. The microcontroller can be further operative to determine an HVACwiring scheme based on the received insertion sensing signals, implementa power scheme based on the determined HVAC wiring scheme, and provide aselection signal to the control node based on the determined HVAC wiringscheme, the HVAC call signal, and the implemented power scheme.

In yet another embodiment, a thermostat for use in connection with aHVAC system is provided. The HVAC system can be a single circuit system,a multiple circuit system, or a common wire system. The thermostat caninclude insertion sensing circuitry operative to provide insertionsensing signals indicative of which HVAC system is connected to thethermostat and control circuitry. The control circuitry can be operativeto receive the insertion sensing signals and engage in single circuitpower stealing, multi-circuit power stealing, or common wire powerutilization for obtaining power from the HVAC system based on thereceived insertion sensing signals.

A further understanding of the nature and advantages of the embodimentsdiscussed herein may be realized by reference to the remaining portionsof the specification and the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram of an enclosure with an HVAC system, according tosome embodiments;

FIG. 2 is a diagram of an HVAC system, according to some embodiments;

FIG. 3A is a schematic block diagram that provides an overview of somecomponents inside a thermostat, according to some embodiments;

FIG. 3B is a block diagram of some circuitry of a thermostat, accordingto some embodiments;

FIGS. 4A-4C schematically illustrate the use of auto-switchingconnectors being used to automatically select a source for powerharvesting, according to some embodiments;

FIG. 5 is a schematic of a half-bridge sense circuit, according to someembodiments;

FIGS. 6A-6B are schematics showing the high voltage buck, bootstrap LDOand battery LDO power circuitry, according to some embodiments;

FIG. 6C shows a battery charging circuit and rechargeable battery,according to some embodiments;

FIG. 7 illustrates an exploded perspective view of a versatile sensingand control unit (VSCU unit) and an HVAC-coupling wall dock according toan embodiment;

FIGS. 8A-8B illustrates conceptual diagrams of HVAC-coupling wall docks,according to some embodiments;

FIGS. 9A-9B illustrate a thermostat having a user-friendly interface,according to some embodiments;

FIG. 9C illustrates a cross-sectional view of a shell portion of a frameof the thermostat of FIGS. 9A-9B, according to some embodiments;

FIGS. 10A-10B illustrate exploded front and rear perspective views,respectively, of a thermostat with respect to its two main components,which are the head unit and the back plate, according to someembodiments;

FIGS. 11A-11B illustrate exploded front and rear perspective views,respectively, of the head unit with respect to its primary components,according to some embodiments;

FIGS. 12A-12B illustrate exploded front and rear perspective views,respectively, of the head unit frontal assembly with respect to itsprimary components, according to some embodiments;

FIGS. 13A-13B illustrate exploded front and rear perspective views,respectively, of the backplate unit with respect to its primarycomponents, according to some embodiments;

FIG. 14 illustrates a perspective view of a partially assembled headunit front, according to some embodiments;

FIG. 15 illustrates a head-on view of the head unit circuit board,according to an embodiment;

FIG. 16 illustrates a rear view of the backplate circuit board,according to an embodiment;

FIGS. 17A-17C illustrate conceptual examples of the sleep-wake timingdynamic, at progressively larger time scales; according to anembodiment;

FIG. 18 illustrates a self-descriptive overview of the functionalsoftware, firmware, and/or programming architecture of the head unitmicroprocessor, according to an embodiment;

FIG. 19 illustrates a self-descriptive overview of the functionalsoftware, firmware, and/or programming architecture of the backplatemicrocontroller, according to an embodiment;

FIG. 20 illustrates a schematic view of a thermostat according to anembodiment;

FIG. 21 illustrates a schematic view of another thermostat according toan embodiment;

FIG. 22 shows a flowchart showing illustrative steps for operating anHVAC system using a thermostat, according to an embodiment;

FIG. 23 shows a simplified illustrative schematic view of portions ofthe thermostat in FIG. 21 wired to a single circuit system, according toan embodiment;

FIGS. 24A and 24B show simplified illustrative schematic views ofportions of the thermostat in FIG. 21 wired to a multiple circuitsystem, according to an embodiment; and

FIG. 25 shows a simplified illustrative schematic view of portions ofthe thermostat in FIG. 21 wired to a common wire circuit system,according to an embodiment.

DETAILED DESCRIPTION OF THE INVENTION

In the following detailed description, for purposes of explanation,numerous specific details are set forth to provide a thoroughunderstanding of the various embodiments of the present invention. Thoseof ordinary skill in the art will realize that these various embodimentsof the present invention are illustrative only and are not intended tobe limiting in any way. Other embodiments of the present invention willreadily suggest themselves to such skilled persons having the benefit ofthis disclosure.

In addition, for clarity purposes, not all of the routine features ofthe embodiments described herein are shown or described. One of ordinaryskill in the art would readily appreciate that in the development of anysuch actual embodiment, numerous embodiment-specific decisions may berequired to achieve specific design objectives. These design objectiveswill vary from one embodiment to another and from one developer toanother. Moreover, it will be appreciated that such a development effortmight be complex and time-consuming but would nevertheless be a routineengineering undertaking for those of ordinary skill in the art havingthe benefit of this disclosure.

It is to be appreciated that while one or more embodiments are describedfurther herein in the context of typical HVAC systems used in aresidential home, such as single-family residential home, the scope ofthe present teachings is not so limited. More generally, thermostatsaccording to one or more of the preferred embodiments are applicable fora wide variety of enclosures having one or more HVAC systems including,without limitation, duplexes, townhomes, multi-unit apartment buildings,hotels, retail stores, office buildings and industrial buildings.Further, it is to be appreciated that while the terms user, customer,installer, homeowner, occupant, guest, tenant, landlord, repair person,and the like may be used to refer to the person or persons who areinteracting with the thermostat or other device or user interface in thecontext of one or more scenarios described herein, these references areby no means to be considered as limiting the scope of the presentteachings with respect to the person or persons who are performing suchactions.

Provided according to one or more embodiments are systems, methods,computer program products, and related business methods for controllingone or more HVAC systems based on one or more versatile sensing andcontrol units (VSCU units), each VSCU unit being configured and adaptedto provide sophisticated, customized, energy-saving HVAC controlfunctionality while at the same time being visually appealing,non-intimidating, elegant to behold, and delightfully easy to use. Theterm “thermostat” is used hereinbelow to represent a particular type ofVSCU unit (Versatile Sensing and Control) that is particularlyapplicable for HVAC control in an enclosure. Although “thermostat” and“VSCU unit” may be seen as generally interchangeable for the contexts ofHVAC control of an enclosure, it is within the scope of the presentteachings for each of the embodiments hereinabove and hereinbelow to beapplied to VSCU units having control functionality over measurablecharacteristics other than temperature (e.g., pressure, flow rate,height, position, velocity, acceleration, capacity, power, loudness,brightness) for any of a variety of different control systems involvingthe governance of one or more measurable characteristics of one or morephysical systems, and/or the governance of other energy or resourceconsuming systems such as water usage systems, air usage systems,systems involving the usage of other natural resources, and systemsinvolving the usage of various other forms of energy.

FIG. 1 is a diagram illustrating an exemplary enclosure using athermostat 110 implemented in accordance with the present invention forcontrolling one or more environmental conditions. For example, enclosure100 illustrates a single-family dwelling type of enclosure using alearning thermostat 110 (also referred to for convenience as “thermostat110”) for the control of heating and cooling provided by an HVAC system120. Alternate embodiments of the present invention may be used withother types of enclosures including a duplex, an apartment within anapartment building, a light commercial structure such as an office orretail store, or a structure or enclosure that is a combination of theseand other types of enclosures.

Some embodiments of thermostat 110 in FIG. 1 incorporate one or moresensors to gather data from the environment associated with enclosure100. Sensors incorporated in thermostat 110 may detect occupancy,temperature, light and other environmental conditions and influence thecontrol and operation of HVAC system 120. Sensors incorporated withinthermostat 110 do not protrude from the surface of the thermostat 110thereby providing a sleek and elegant design that does not drawattention from the occupants in a house or other enclosure. As a result,thermostat 110 and readily fits with almost any décor while adding tothe overall appeal of the interior design.

As used herein, a “learning” thermostat refers to a thermostat, or oneof plural communicating thermostats in a multi-thermostat network,having an ability to automatically establish and/or modify at least onefuture setpoint in a heating and/or cooling schedule based on at leastone automatically sensed event and/or at least one past or current userinput.

As used herein, a “primary” thermostat refers to a thermostat that iselectrically connected to actuate all or part of an HVAC system, such asby virtue of electrical connection to HVAC control wires (e.g. W, G, Y,etc.) leading to the HVAC system.

As used herein, an “auxiliary” thermostat refers to a thermostat that isnot electrically connected to actuate an HVAC system, but that otherwisecontains at least one sensor and influences or facilitates primarythermostat control of an HVAC system by virtue of data communicationswith the primary thermostat.

In one particularly useful scenario, the thermostat 110 is a primarylearning thermostat and is wall-mounted and connected to all of the HVACcontrol wires, while the remote thermostat 112 is an auxiliary learningthermostat positioned on a nightstand or dresser, the auxiliary learningthermostat being similar in appearance and user-interface features asthe primary learning thermostat, the auxiliary learning thermostatfurther having similar sensing capabilities (e.g., temperature,humidity, motion, ambient light, proximity) as the primary learningthermostat, but the auxiliary learning thermostat not being connected toany of the HVAC wires. Although it is not connected to any HVAC wires,the auxiliary learning thermostat wirelessly communicates with andcooperates with the primary learning thermostat for improved control ofthe HVAC system, such as by providing additional temperature data at itsrespective location in the enclosure, providing additional occupancyinformation, providing an additional user interface for the user, and soforth.

It is to be appreciated that while certain embodiments are particularlyadvantageous where the thermostat 110 is a primary learning thermostatand the remote thermostat 112 is an auxiliary learning thermostat, thescope of the present teachings is not so limited. Thus, for example,while certain initial provisioning methods that automatically pairassociate a network-connected thermostat with an online user account areparticularly advantageous where the thermostat is a primary learningthermostat, the methods are more generally applicable to scenariosinvolving primary non-learning thermostats, auxiliary learningthermostats, auxiliary non-learning thermostats, or other types ofnetwork-connected thermostats and/or network-connected sensors. By wayof further example, while certain graphical user interfaces for remotecontrol of a thermostat may be particularly advantageous where thethermostat is a primary learning thermostat, the methods are moregenerally applicable to scenarios involving primary non-learningthermostats, auxiliary learning thermostats, auxiliary non-learningthermostats, or other types of network-connected thermostats and/ornetwork-connected sensors. By way of even further example, while certainmethods for cooperative, battery-conserving information polling of athermostat by a remote cloud-based management server may be particularlyadvantageous where the thermostat is a primary learning thermostat, themethods are more generally applicable to scenarios involving primarynon-learning thermostats, auxiliary learning thermostats, auxiliarynon-learning thermostats, or other types of network-connectedthermostats and/or network-connected sensors.

Enclosure 100 further includes a private network accessible bothwirelessly and through wired connections and may also be referred to asa Local Area Network or LAN. Network devices on the private networkinclude a computer 124, thermostat 110 and remote thermostat 112 inaccordance with some embodiments of the present invention. In oneembodiment, the private network is implemented using an integratedrouter 122 that provides routing, wireless access point functionality,firewall and multiple wired connection ports for connecting to variouswired network devices, such as computer 124. Each device is assigned aprivate network address from the integrated router 122 eitherdynamically through a service like Dynamic Host Configuration Protocol(DHCP) or statically through actions of a network administrator. Theseprivate network addresses may be used to allow the devices tocommunicate with each directly over the LAN. Other embodiments mayinstead use multiple discrete switches, routers and other devices (notshown) to perform more other networking functions in addition tofunctions as provided by integrated router 122.

Integrated router 122 further provides network devices access to apublic network, such as the Internet, provided enclosure 100 has aconnection to the public network generally through a cable-modem, DSLmodem and an Internet service provider or provider of other publicnetwork service. Public networks like the Internet are sometimesreferred to as a Wide-Area Network or WAN. In the case of the Internet,a public address is assigned to a specific device allowing the device tobe addressed directly by other devices on the Internet. Because thesepublic addresses on the Internet are in limited supply, devices andcomputers on the private network often use a router device, likeintegrated router 122, to share a single public address through entriesin Network Address Translation (NAT) table. The router makes an entry inthe NAT table for each communication channel opened between a device onthe private network and a device, server, or service on the Internet. Apacket sent from a device on the private network initially has a“source” address containing the private network address of the sendingdevice and a “destination” address corresponding to the public networkaddress of the server or service on the Internet. As packets pass fromwithin the private network through the router, the router replaces the“source” address with the public network address of the router and a“source port” that references the entry in the NAT table. The server onthe Internet receiving the packet uses the “source” address and “sourceport” to send packets back to the router on the private network which inturn forwards the packets to the proper device on the private networkdoing a corresponding lookup on an entry in the NAT table.

Entries in the NAT table allow both the computer device 124 and thethermostat 110 to establish individual communication channels with athermostat management system (not shown) located on a public networksuch as the Internet. In accordance with some embodiments, a thermostatmanagement account on the thermostat management system enables acomputer device 124 in enclosure 100 to remotely access thermostat 110.The thermostat management system passes information from the computerdevice 124 over the Internet and back to thermostat 110 provided thethermostat management account is associated with or paired withthermostat 110. Accordingly, data collected by thermostat 110 alsopasses from the private network associated with enclosure 100 throughintegrated router 122 and to the thermostat management system over thepublic network. Other computer devices not in enclosure 100 such asSmartphones, laptops and tablet computers (not shown in FIG. 1) may alsocontrol thermostat 110 provided they have access to the public networkwhere the thermostat management system and thermostat management accountmay be accessed. Further details on accessing the public network, suchas the Internet, and remotely accessing a thermostat like thermostat 110in accordance with embodiments of the present invention is described infurther detail later herein.

In some embodiments, thermostat 110 may wirelessly communicate withremote thermostat 112 over the private network or through an ad hocnetwork formed directly with remote thermostat 112. During communicationwith remote thermostat 112, thermostat 110 may gather informationremotely from the user and from the environment detectable by the remotethermostat 112. For example, remote thermostat 112 may wirelesslycommunicate with the thermostat 110 providing user input from the remotelocation of remote thermostat 112 or may be used to display informationto a user, or both. Like thermostat 110, embodiments of remotethermostat 112 may also include sensors to gather data related tooccupancy, temperature, light and other environmental conditions. In analternate embodiment, remote thermostat 112 may also be located outsideof the enclosure 100.

FIG. 2 is a schematic diagram of an HVAC system controlled using athermostat designed in accordance with embodiments of the presentinvention. HVAC system 120 provides heating, cooling, ventilation,and/or air handling for an enclosure 100, such as a single-family homedepicted in FIG. 1. System 120 depicts a forced air type heating andcooling system, although according to other embodiments, other types ofHVAC systems could be used such as radiant heat based systems, heat-pumpbased systems, and others.

In heating, heating coils or elements 242 within air handler 240 providea source of heat using electricity or gas via line 236. Cool air isdrawn from the enclosure via return air duct 246 through filter 270,using fan 238 and is heated through heating coils or elements 242. Theheated air flows back into the enclosure at one or more locations viasupply air duct system 252 and supply air registers such as register250. In cooling, an outside compressor 230 passes a gas such as Freonthrough a set of heat exchanger coils 244 to cool the gas. The gas thengoes through line 232 to the cooling coils 234 in the air handler 240where it expands, cools and cools the air being circulated via fan 238.A humidifier 254 may optionally be included in various embodiments thatreturns moisture to the air before it passes through duct system 252.Although not shown in FIG. 2, alternate embodiments of HVAC system 120may have other functionality such as venting air to and from theoutside, one or more dampers to control airflow within the duct system252 and an emergency heating unit. Overall operation of HVAC system 120is selectively actuated by control electronics 212 communicating withthermostat 110 over control wires 248.

Referring to FIG. 3A, a schematic block diagram provides an overview ofsome components inside a thermostat in accordance with embodiments ofthe present invention. Thermostat 308 is similar to thermostat 112 inFIG. 1 except that thermostat 308 also illustrates and highlightsselected internal components including a Wi-Fi module 312 and antenna, ahead unit processor 314 with associated memory 315, a backplateprocessor 316 with associated memory, and sensors 322 (e.g.,temperature, humidity, motion, ambient light, proximity). In oneembodiment, head unit processor 314 can be a Texas Instruments AM3703Sitara ARM microprocessor while backplate processor 316, which may bemore specifically referenced to as a “microcontroller”, can be a TexasInstruments MSP430F microcontroller. Further details regarding thephysical placement and configuration of the thermostat head unit,backplate, and other physical elements are described in the commonlyassigned U.S. Ser. No. 13/199,108, supra.

For some embodiments, the backplate processor 316 is a very low-powerdevice that, while having some computational capabilities, issubstantially less powerful than the head unit processor 314. Thebackplate processor 316 is coupled to, and responsible for polling on aregular basis, most or all of the sensors 322 including the temperatureand humidity sensors, motion sensors, ambient light sensors, andproximity sensors. For sensors 322 that may not be located on thebackplate hardware itself but rather are located in the head unit,ribbon cables or other electrical connections between the head unit andbackplate are provided for this purpose. Notably, there may be othersensors (not shown) for which the head unit processor 314 isresponsible, with one example being a ring rotation sensor that sensesthe user rotation of an outer ring of the thermostat. Each of the headunit processor 314 and backplate processor 316 is capable of enteringinto a “sleep” state, and then “waking up” to perform various tasks.

The backplate processor 316, which in some embodiments will have alow-power sleep state that corresponds simply to a lower clock speed,generally enters into and out of its sleep mode substantially more oftenthan does the more powerful head unit processor 314. The backplateprocessor 316 is capable of waking up the head unit processor 314 fromits sleep state. For one preferred embodiment directed to optimalbattery conservation, the head unit processor 314 is allowed to sleepwhen its operations are not being called for, while the backplateprocessor 316 performs polling of the sensors 322 on an ongoing basis,maintaining the sensor results in memory 317. The backplate processor316 will wake up the head unit processor 314 in the event that (i) thesensor data indicates that an HVAC operation may be called for, such asif the current temperature goes below a currently active heatingsetpoint, or (ii) the memory 317 gets full and the sensor data needs tobe transferred up to the head unit processor 314 for storage in thememory 315. The sensor data can then be pushed up to the cloud server(thermostat management server) during a subsequent active communicationsession between the cloud server and the head unit processor 314.

In the case of Wi-Fi module 312, one embodiment may be implemented usingMurata Wireless Solutions LBWA19XSLZ module, which is based on the TexasInstruments WL1270 chipset supporting the 802.11b/g/n WLAN standard.Embodiments of the present invention configure and program Wi-Fi module312 to allow thermostat 308 to enter into a low power or “sleep” mode toconserve energy until one or several events occurs. For example, in someembodiments the Wi-Fi module 312 may leave this low power mode when auser physically operates thermostat 308, which in turn may also causeactivation of both head-unit processor 314 and backplate processor 316for controlling functions in head-unit and backplate portions ofthermostat 110.

It is also possible for Wi-Fi module 312 to wake from a low power modeat regular intervals in response to a beacon from wireless access point372. To conserve energy, Wi-Fi module 312 may briefly leave the lowpower mode to acknowledge the beacon as dictated by the appropriatewireless standard and then return to a low power mode without activatingthe processors or other components of thermostat 308 in FIG. 3A. In analternative embodiment, Wi-Fi module 312 may also respond to the beaconby awaking briefly and then activating backplate processor 316, headunit processor 314, or other portions of thermostat 308 to gather datathrough sensors 322 and store the results in a data log 326 with a timestamp, event type and corresponding data listed for future reference. Inaccordance with one embodiment, backplate processor 316 may collect datain data log 326 and store in memory 320 for a period of time or untilthe log reaches a maximum predetermined size. At that point, thebackplate processor 316 may wake head unit processor 314 to coordinatean upload of the data log 326 stored in memory 320 over a publicnetwork, such as the Internet, to cloud-based management server 516.Uploading data log 326 less frequently saves time and energy associatedwith more frequent transmission of individual records or log entries.

In yet another embodiment, Wi-Fi module 312 may selectively filter anincoming data packet to determine if the header is merely anacknowledgement packet (i.e., a keep-alive packet) or contains a payloadthat needs further processing. If the packet contains only a header andno payload, the Wi-Fi module 312 may be configured to either ignore thepacket or send a return acknowledgement to the thermostat managementsystem or other source of the packet received.

In further embodiments, Wi-Fi module 312 may be used to establishmultiple communication channels between thermostat 112 and a cloud-basedmanagement server as will be described and illustrated later in thisdisclosure. As previously described, thermostat 112 uses multiplecommunication channels to receive different types of data classifiedwith different levels of priority. In one embodiment, Wi-Fi module 312may be programmed to use one or more filters and a wake-on-LAN featureto then selectively ignore or discard data arriving over one or more ofthese communication channels. For example, low-priority data arrivingover a port on Wi-Fi module 312 may be discarded by disabling thecorresponding wake-on-LAN feature associated with the port. This allowsthe communication channel to continue to operate yet conserves batterypower by discarding or ignoring the low-priority packets.

Operation of the microprocessors 314, 316, Wi-Fi module 312, and otherelectronics may be powered by a rechargeable battery (not shown) locatedwithin the thermostat 110. In some embodiments, the battery is rechargeddirectly using 24 VAC power off a “C” wire drawn from the HVAC system oran AC-DC transformer coupled directly into the thermostat 110.Alternatively, one or more different types of energy harvesting may alsobe used to recharge the internal battery if these direct methods are notavailable as described, for example, in U.S. Ser. No. 13/034,678, supra,and U.S. Ser. No. 13/267,871, supra. Embodiments of the presentinvention communicate and operate the thermostat 110 in a manner thatpromotes efficient use of the battery while also keeping the thermostatoperating at a high level of performance and responsiveness controllingthe HVAC system. Some embodiments may use the battery-level charge andthe priority or relative importance of a communication to determine whena thermostat management system located on a public network such as theInternet may communicate with the thermostat 110. Further details on thecommunication methods and system used in accordance with theseembodiments are described in detail later herein.

Turning now to power harvesting methods and systems, FIG. 3B is a blockdiagram of some circuitry of a thermostat, according to someembodiments. Circuitry 300, according to some embodiments, is abackplate of a thermostat. A number of HVAC wires can be attached usingHVAC terminals 372. One example of which is the W1 terminal 374. Eachterminal is used to control an HVAC function. According to someembodiments, each of the wires from the terminals W1, W2, Y1, Y2, G,O/B, AUX and E is connected to separate isolated FET drives 370. Thecommon HVAC functions for each of the terminals are: W1 and W2 heating;Y1 and Y2 for cooling; G for fan; O/B for heatpumps; and E for emergencyheat. Note that although the circuitry 300 is able control 8 functionsusing the isolated FET drives 370, according to some embodiments, otherfunctions, or fewer functions can be controlled. For example circuitryfor a more simply equipped HVAC system may only have a single heating(W), and single cooling (Y) and a fan (G), in which case there wouldonly be three isolated FET drives 370. According to a preferredembodiment, 5 FET drives 370 are provided, namely heating (W), cooling(Y), fan (G), auxiliary (AUX) and compressor direction (O/B). Not shownare the circuit returns such as RH (return for heat) and RC (return forcooling). According to some embodiments the thermostat can control ahumidifier and/or de-humidifier. Further details relating to isolatedFET drives 370 are described in co-pending U.S. patent application Ser.No. 13/034,674, entitled “Thermostat Circuitry for Connection to HVACSystems,” supra, which is incorporated herein by reference.

The HVAC functions are controlled by the HVAC control general purposeinput/outputs (GPIOs) 322 within microcontroller (MCU) 320. MCU 320 is ageneral purpose microcontroller such as the MSP430 16-bit ultra-lowpower MCU available from Texas Instruments. MCU 320 communicates withthe head unit via Head Unit Interface 340. The head unit together withthe backplate make up the thermostat. The head unit has user interfacecapability such that it can display information to a user via an LCDdisplay and receive input from a user via buttons and/or touch screeninput devices. According to some embodiments, the head unit has networkcapabilities for communication to other devices either locally or overthe internet. Through such network capability, for example, thethermostat can send information and receive commands and setting from acomputer located elsewhere inside or outside of the enclosure. The MCUdetects whether the head unit is attached to the backplate via head unitdetect 338.

Clock 342 provides a low frequency clock signal to MCU 320, for example32.768 kHz. According to some embodiments there are two crystaloscillators, one for high frequency such as 16 MHz and one for the lowerfrequency. Power for MCU 320 is supplied at power input 344 at 3.0 V.Circuitry 336 provides wiring detection, battery measurement, and buckinput measurement. A temperature sensor 330 is provided, and accordingto some embodiments and a humidity sensor 332 are provided. According tosome embodiments, one or more other sensors 334 are provided such as:pressure, proximity (e.g. using infrared), ambient light, andpyroelectric infrared (PIR).

Power circuitry 350 is provided to supply power. According to someembodiments, when the thermostat is first turned on with insufficientbattery power, a bootstrap power system is provided. A high voltage lowdropout voltage regulator (LDO) 380 provides 3.0 volts of power for thebootstrap of the MCU 320. The bootstrap function can be disabled underMCU control but according to some embodiments the bootstrap function isleft enabled to provide a “safety net” if the head unit supply vanishesfor any reason. For example, if the head-unit includes the re-chargeablebattery 384 and is removed unexpectedly, the power would be lost and thebootstrap function would operate. The input to this Bootstrap LDO 380 isprovided by connectors and circuitry 368 that automatically selectspower from common 362 (highest priority), cool 366 (lower priority); orheat (lowest priority) 364.

In normal operation, a 3.0 volt primary LDO 382 powers the backplatecircuitry and itself is powered by VCC Main. According to someembodiments, high voltage buck 360 is provided as a second supply in thebackplate. The input to this supply is the circuitry 368. According tosome embodiments, the high voltage buck 380 can supply a maximum of 100mA at 4.5 v. According to some embodiments, the VCC main and the PrimaryLDO 382 can be powered by a rechargeable battery (shown in FIG. 7) incases where there is no alternative power source (such as the highvoltage buck or USB power, for example).

FIGS. 4A-C schematically illustrate the use of auto-switching connectorsbeing used to automatically select a source for power harvesting,according to some embodiments. The connectors 362, 364, and 366 areconnectors as shown in FIG. 3B. For further details regarding preferredautomatically switching connectors, see co-pending U.S. patentapplication Ser. No. 13/034,666, entitled “Thermostat Wiring Connector”filed on even date herewith and incorporated herein by reference. Theconnector 362 is used for connection to an HVAC “C” (common) wire andincludes two switched pairs of normally closed secondary conductors 410and 412. The connector 366 is used for connection to an HVAC “Y”(cooling) wire and includes one switched pair of normally closedsecondary conductors 454. The connector 364 is used for connection to anHVAC “W” (heating) wire. Note that although not shown in FIGS. 4A-C, oneor more additional pairs of switched secondary conductors can beprovided with any of the connectors 362, 366 and 365, such as could beused for the purpose of electronically detecting the presence of an HVACsystem wire to the connector. Power harvesting circuitry 460 is used tosupply power to the thermostat and is also connected to the Rc wire 462(or according to other embodiment the Rh wire). For example, the powerharvesting circuitry 460 can include the HV buck 360 and Bootstrap LDO380 as shown in and described with respect to FIGS. 3 and 6A-B.

FIG. 4A shows the case of the switches 454, 410 and 412 when no C wireand no Y wire is attached. In this case all of the switches 454, 410 and412 are closed and the power harvesting circuitry 460 is connected atinput 464 with the W wire via circuit paths 420, 422 and 426. FIG. 4Bshows the case of the switches 454, 410 and 412 when no C wire isattached but there is a Y wire attached. In this case switches 410 and412 are closed but switch 454 is opened due to the presence of the Ywire. In this case the power harvesting circuitry 460 is connected atinput 464 with the Y wire via circuit paths 424 and 428. FIG. 4C showsthe case of the switches 454, 410, and 412, when both C and Y wires areattached. In this case all the switches 454, 410 and 412 are open andthe power harvesting circuitry 460 is connected at input 464 with the Cwire via circuit path 430. Note that the case of a connection of C and Wwires and no Y wire is not shown but that in this case the W wire wouldnot be connected to circuitry 420 since switch 410 would be open. Thus,through the use of circuitry and the connectors shown, the powerharvesting circuitry is automatically switched so as to use connectionsto C, Y and W wires in decreasing order of priority. Preferably, the Cwire is the highest priority as this ordinarily provides the best powersource, if available. Note that according to some embodiments, the Y andW priorities are reversed to make W higher priority than Y.

FIG. 5 is a schematic of a half-bridge sense circuit, according to someembodiments. Circuit 500 provides voltage sensing, clipped to 3.0 volts,for presence detection and current sensing. At inputs 502, 504 and 506are the 24VAC waveforms from three of the HVAC circuits. In the caseshown in FIG. 5, inputs 502, 504 and 506 are for HVAC W1, HVAC Y1 andHVAC G, respectively. The sense input bias buffer 550 is provided asshown. Note that a voltage divider is used in each case that takes thevoltage from 24 volts to approximately 4 volts. Clamp diodes 520 a, 520b and 520 c ensure that the voltage goes no higher or lower than therange of the microcontroller 320 (shown in FIG. 3B). The Sense outputs530, 532 and 534 are connected to the microcontroller 320 so that themicrocontroller 320 can sense the presence of a signal on the HVAClines. The circuits are repeated for the other HVAC lines so that themicrocontroller can detect signals on any of the HVAC lines.

FIGS. 6A-B are schematics showing the high voltage buck, bootstrap LDOand battery LDO power circuitry, according to some embodiments. FIG. 6Ashows the input 464 from the connector selected power, which correspondsto input 464 to power circuitry 460 in FIG. 4. The diodes 632 are usedto rectify the AC power signal from the HVAC power transformer wire thatis selected by the connector circuitry shown in FIG. 4. When thethermostat is installed in a building having two HVAC powertransformers, such as may be the case when an existing HVAC heating-onlysystem is upgraded to add an HVAC cooling system. In such cases, thereare two power wires from the HVAC system, often called “Rh” the powerwire directly from the heating system transformer, and “Rc” the powerwire directly from the cooling transformer. Input 462 is from a terminalconnected to the Rc wire. According to some embodiments, the Rc and Rhterminals are switched using automatic switching or other jumperlessdesign, as shown and described in co-pending U.S. patent applicationSer. No. 13/034,674, entitled “Thermostat Circuitry for Connection toHVAC Systems,” filed Feb. 24, 2011 and incorporated herein by reference.

Rectified input 624 is input to the high voltage buck circuit 610,according to some embodiments. In buck circuit 610, which corresponds tohigh voltage buck 360 in FIG. 3B, the voltage on the input capacitors612, 614 and 616 of high voltage buck 610 can be measured by the MCU 320(of FIG. 3B) at node 620, allowing the MCU to momentarily open the W1 orY1 contacts during an “enabled” or “on” phase in order to recharge thebuck input capacitors 612, 614 and 616 and continue power harvesting.According to some embodiments, the same HVAC circuit (e.g. heating orcooling) is used for power harvesting, whether or not there is more thanone HVAC function in the system. According to some other embodiments,when the thermostat is used with an HVAC system having two circuits(e.g. heating and cooling), the system will harvest power from thenon-activated circuit. In cases where a common wire is available fromthe HVAC power transformer, the system preferably does not power harvestat all from the heating and cooling circuits. According to someembodiments, the step down converter 630 is a high efficiency, highvoltage 100 mA synchronous step-down converter such as the LTC3631 fromLinear Technology. According to some embodiments, inductor 642 is a 100uH power inductor such as the MOS6020 from Coilcraft. According to someembodiments, one or more other types of elements in addition to orinstead of input capacitors 612, 614 and 616 are used to storeelectrical energy during power harvesting when the HVAC function isactive (or “on”). For example, magnetic elements such as inductorsand/or transformers can be used.

In order to control the HVAC functions, the HVAC function wire isshorted to the return or power wire. For example, in the case ofheating, the W wire is shorted to the Rh (or R or Rc depending on theconfiguration). In the case of cooling the Y wire is shorted to the Rc(or R or Rh depending on the configuration). By shorting these twowires, the 24 VAC transformer is placed in series with a relay thatcontrols the HVAC function. However, for power harvesting, a problem isthat when these wires are shorted, there is no voltage across them, andwhen open, there is no current flow. Since power equals voltagemultiplied by current, if either quantity is zero the power that can beextracted is zero. According to some embodiments, the power harvestingcircuitry allows power to be taken from the two wires in both the statesof HVAC—the HVAC “on” and the HVAC “off”.

In the HVAC “off” state, some energy can be harvested from these twowires by taking less energy than would cause the of the relay to turnon, which would cause the HVAC function to erroneously turn on. Based ontesting, it has been found that HVAC functions generally do not turn onwhen (0.040 A*4.5V)=0.180 watts is extracted at the output. So after theinput diodes, capacitors, and switching regulator, this allows us totake 40 mA at 4.5 volts from these wires without turning on the HVACsystem.

In the HVAC “on” state, the two wires must be connected together toallow current to flow, which turns on the HVAC relay. This, however,shorts out the input supply, so our system does not get any power whenthe HVAC “on” switch is closed. To get around this problem, the voltageis monitored on the capacitors 612, 614 and 616 at the input switchingpower supply node 620. When the voltage on these capacitors “C_(in)”drops close to the point at which the switching power supply would “Dropout” and lose output regulation, for example at about +8 Volts, the HVAC“on” switch is turned off and C_(in) is charged. During the time thatC_(in) is charging, current is still flowing in the HVAC relay, so theHVAC relay stays on. When the C_(in) capacitor voltages increases someamount, for example about +16 Volts, the HVAC “on” switch is closedagain, C_(in) begins to discharge while it feeds the switchingregulator, and current continues to flow in the HVAC relay. Note thatC_(in) is not allowed to discharge back to the HVAC “on” switch due toinput diodes 632. When the voltage on C_(in) drops to about +8 Volts theHVAC “on” switch is turned off and the process repeats. This continuesuntil the system tells the HVAC “on” switch to go off because HVAC is nolonger needed. According to some embodiments, the ability of the HVAC“on” switch to turn on and off relatively quickly is provided bycircuitry 450 as shown in and described with respect to FIG. 4 ofco-pending U.S. patent application Ser. No. 13/034,674, entitled“Thermostat Circuitry for Connection to HVAC Systems,” supra, which isincorporated herein by reference.

According to some embodiments, one or more alternative power harvestingtechniques are used. For example, rather than having the HVAC “on”switch turn on when the voltage on C_(in) reaches a certain point, itthe system might turn off the “HVAC “on” switch for a predeterminedperiod of time instead. According to some embodiments, power harvestingis enhanced by synchronizing the power harvesting with the AC currentwaveform.

FIG. 6B is a schematic of high voltage low dropout voltage regulatorsused to provide bootstrap power and battery, according to someembodiments. The bootstrap LDO circuitry 680, and battery LDO circuitrycorrespond to the bootstrap LDO 380 and battery LDO 382 in FIG. 3respectively. Rectified input 624 is input to bootstrap circuit 680.According to some embodiments, regulator 670 is low-dropout linearregulator such as the TPS79801 from Texas Instruments. The output power690 is provided to the backplate at 3.0V. The bootstrap disable signal680 can be used to disable the bootstrap power unit, as shown. The input660 comes from VCC main, which can be, for example, from therechargeable battery. According to some embodiments, the low dropoutregulator 662 is a low quiescent current device designed forpower-sensitive applications such as the TLV70030 from TexasInstruments.

FIG. 6C shows a battery charging circuit 675 and a rechargeable battery650, according to some embodiments. The charger 673 is used to chargethe lithium-ion battery 650. In general, li-ion battery capacity dependson what voltage the battery is charged to, and the cycle life depends onthe charged voltage, how fast the battery is charged and the temperatureduring which the battery is charged. Ordinarily, Li-ion batteries arecharged at about 4.2V. In some cases the charging voltage is even higherin an attempt to gain greater capacity, but at the expense of decreasedcycle life. However, in the case of the rechargeable battery 650 for usewith a wall-mounted thermostat, a greater cycle life is preferred overcapacity. High capacity is generally not needed since charging power isavailable via the power harvesting circuitry, and greater cycle life ispreferred since user replacement may be difficult or unavailable. Thus,according to some embodiments, a low charging speed, low final floatvoltage and reduced charging temperature range is preferred. Accordingto some embodiments, a final float voltage of between 3.9V and 4.1V isused. According to some embodiments a final float voltage of less than4.0V is used, such as 3.95V. According to some embodiments, the ratio ofcharge current to total capacity “C” is also controlled, such ascharging the battery to 0.2 C (0.2 times the rated capacity) to providebetter cycle life than a higher ratio. According to some embodiments,using a lower charging current aids in avoiding unintended tripping ofthe HVAC relay.

According to some embodiments, charger 673 is a USB power manager andli-ion battery charger such as the LTC4085-3 from Linear Technology.Backplate voltage 671 is input to charger 673. The circuitry 672 is usedto select the charging current. In particular the value of resistor 674(24.9 k) in parallel with resistor 634 (16.9 k) in combination with theinputs Double Current 638 and High Power 628 are used to select thecharging current. If High Power 628 and Double Current 638 are both setto 0, then the charging current is 8.0 mA; if the High Power 628 is setto 0 and Double Current 638 is set to 1, then the charging current is19.9 mA; if the High Power 628 is set to 1 and Double Current 638 is setto 0, then the charging current is 40.1 mA; and if the High Power 628and Double Current 638 are both set to 1, then the charging current is99.3 mA. Resistor 636 is used to set the default charge current. In thecase shown, a 220 k resistor set the default charge current to 227 mA.According to some embodiments, a charge temperature range of 0-44degrees C. is set via the Thermistor Monitoring Circuits.

According to some embodiments, the thermostat is capable of beingpowered by a USB power supply. This could be supplied by a user, forexample, by attaching the thermostat via a USB cable to a computer oranother USB power supply. In cases where USB power supply is available,it is selected as the preferred power source for the thermostat and canbe used to recharge the rechargeable battery. According to someembodiments, a charge current of about 227 mA is used when a USB supplysource is available; a charge current of about 100 mA is used when anHVAC common wire is present; and a charge current of between about 20-40mA is used when power is harvested from an HVAC heating and/or coolingcircuit.

FIG. 7 illustrates an exploded perspective view of a thermostat or VSCU(versatile sensing and control unit) 700 and an HVAC-coupling wall dock702 according to an embodiment. For first-time customers who are goingto be replacing their old thermostat, the VSCU unit 700 is provided incombination with HVAC-coupling wall dock 702. The HVAC-coupling walldock 702 comprises mechanical hardware for attaching to the wall andelectrical terminals for connecting to the HVAC wiring 298 that will beextending out of the wall in a disconnected state when the oldthermostat is removed. The HVAC-coupling wall dock 702 is configuredwith an electrical connector 704 that mates to a counterpart electricalconnector 705 in the VSCU 700.

For the initial installation process, the customer (or their handyman,or an HVAC professional, etc.) first installs the HVAC-coupling walldock 702, including all of the necessary mechanical connections to thewall and HVAC wiring connections to the HVAC wiring 298. Once theHVAC-coupling wall dock 702 is installed, which represents the “hardwork” of the installation process, the next task is relatively easy,which is simply to slide the VSCU unit 700 thereover to mate theelectrical connectors 704/705. Preferably, the components are configuredsuch that the HVAC-connecting wall dock 702 is entirely hiddenunderneath and inside the VSCU unit 700, such that only the visuallyappealing VSCU unit 700 is visible.

For one embodiment, the HVAC-connecting wall dock 702 is a relatively“bare bones” device having the sole essential function of facilitatingelectrical connectivity between the HVAC wiring 298 and the VSCU unit700. For another embodiment, the HVAC-coupling wall dock 702 is equippedto perform and/or facilitate, in either a duplicative sense and/or aprimary sense without limitation, one or more of the functionalitiesattributed to the VSCU unit 700 in the instant disclosure, using a setof electrical, mechanical, and/or electromechanical components 706. Oneparticularly useful functionality is for the components 706 to includepower-extraction circuitry for judiciously extracting usable power fromthe HVAC wiring 298, at least one of which will be carrying a 24-volt ACsignals in accordance with common HVAC wiring practice. Thepower-extraction circuitry converts the 24-volt AC signal into DC power(such as at 5 VDC, 3.3 VDC, etc.) that is usable by the processingcircuitry and display components of the main unit 701.

The division and/or duplication of functionality between the VSCU unit700 and the HVAC-coupling wall dock 702 can be provided in manydifferent ways without departing from the scope of the presentteachings. For another embodiment, the components 706 of theHVAC-coupling wall dock 702 can include one or more sensing devices,such as an acoustic sensor, for complementing the sensors provided onthe sensor ring 104 of the VSCU unit 700. For another embodiment, thecomponents 706 can include wireless communication circuitry compatiblewith one or more wireless communication protocols, such as the Wi-Fiand/or ZigBee protocols. For another embodiment, the components 706 caninclude external AC or DC power connectors. For another embodiment, thecomponents 706 can include wired data communications jacks, such as anRJ45 Ethernet jack, an RJ11 telephone jack, or a USB connector.

The docking capability of the VSCU unit 700 according to the embodimentof FIG. 7 provides many advantages and opportunities in both atechnology sense and a business sense. Because the VSCU unit 700 can beeasily removed and replaced by even the most non-technically-savvycustomer, many upgrading and upselling opportunities are provided. Forexample, many different versions of the VSCU unit 700 can be separatelysold, the different versions having different colors, styles, themes,and so forth. Upgrading to a new VSCU unit 700 having more advancedcapabilities becomes a very easy task, and so the customer will bereadily able to take advantage of the newest display technology, sensortechnology, more memory, and so forth as the technology improves overtime.

Provided in accordance with one or more embodiments related to thedocking capability shown in FIG. 7 are further devices and features thatadvantageously promote expandability of the number of sensing andcontrol nodes that can be provided throughout the home. For oneembodiment, a tabletop docking station (not shown) is provided that iscapable of docking to a second instance of the VSCU unit 700, which istermed herein an auxiliary VSCU unit (not shown). The tabletop dockingstation and the auxiliary VSCU unit can be separately purchased by theuser, either at the same time they purchase their original VSCU unit700, or at a later time. The tabletop docking station is similar infunctionality to the HVAC-coupling wall dock 702, except that it doesnot require connection to the HVAC wiring 298 and is convenientlypowered by a standard wall outlet. For another embodiment, instead ofbeing identical to the original VSCU unit 700, the auxiliary VSCU unitcan be a differently labeled and/or differently abled version thereof.

As used herein, the term “primary VSCU unit” refers to one that iselectrically connected to actuate an HVAC system in whole or in part,which would necessarily include the first VSCU unit purchased for anyhome, while the term “auxiliary VSCU unit” refers to one or moreadditional VSCU units not electrically connected to actuate an HVACsystem in whole or in part. An auxiliary VSCU unit, when docked, willautomatically detect the primary VSCU unit and will automatically bedetected by the primary VSCU unit, such as by Wi-Fi or ZigBee wirelesscommunication. Although the primary VSCU unit will remain the soleprovider of electrical actuation signals to the HVAC system, the twoVSCU units will otherwise cooperate in unison for improved controlheating and cooling control functionality, such improvement beingenabled by virtue of the added multi-sensing functionality provided bythe auxiliary VSCU unit, as well as by virtue of the additionalprocessing power provided to accommodate more powerful and precisecontrol algorithms. Because the auxiliary VSCU unit can accept usercontrol inputs just like the primary VSCU unit, user convenience is alsoenhanced. Thus, for example, where the tabletop docking station and theauxiliary VSCU unit are placed on a nightstand next to the user's bed,the user is not required to get up and walk to the location of theprimary VSCU unit if they wish to manipulate the temperature set point,view their energy usage, or otherwise interact with the system.

A variety of different VSCU-compatible docking stations are within thescope of the present teachings. For example, in another embodiment thereis provided an auxiliary wall dock (not shown) that allows an auxiliaryVSCU unit to be mounted on a wall. The auxiliary wall dock is similar infunctionality to the tabletop docking station in that it does notprovide HVAC wiring connections, but does serve as a physical mountingpoint and provides electrical power derived from a standard wall outlet.

For one embodiment, all VSCU units sold by the manufacturer areidentical in their core functionality, each being able to serve aseither a primary VSCU unit or auxiliary VSCU unit as the case requires,although the different VSCU units may have different colors, ornamentaldesigns, memory capacities, and so forth. For this embodiment, the useris advantageously able, if they desire, to interchange the positions oftheir VSCU units by simple removal of each one from its existing dockingstation and placement into a different docking station. Among otheradvantages, there is an environmentally, technically, and commerciallyappealing ability for the customer to upgrade to the newest, latest VSCUdesigns and technologies without the need to throw away the existingVSCU unit. For example, a customer with a single VSCU unit (which isnecessarily serving as a primary VSCU unit) may be getting tired of itscolor or its TFT display, and may be attracted to a newly released VSCUunit with a different color and a sleek new OLED display. For this case,in addition to buying the newly released VSCU, the customer can buy atabletop docking station to put on their nightstand. The customer canthen insert their new VSCU unit into the existing HVAC-coupling walldock, and then take their old VSCU unit and insert it into the tabletopdocking station. Advantageously, in addition to avoiding thewastefulness of discarding the old VSCU unit, there is now a newauxiliary VSCU unit at the bedside that not only provides increasedcomfort and convenience, but that also promotes increased energyefficiency by virtue of the additional multi-sensor information andprocessing power provided.

For other embodiments, different VSCU units sold by the manufacturer canhave different functionalities in terms of their ability to serve asprimary versus auxiliary VSCU units. This may be advantageous from apricing perspective, since the hardware cost of an auxiliary-only VSCUunit may be substantially less than that of a dual-capabilityprimary/auxiliary VSCU unit. In other embodiments there is provideddistinct docking station capability for primary versus auxiliary VSCUunits, with primary VSCU units using one kind of docking connectionsystem and auxiliary VSCU units using a different kind of dockingconnection system. In still other embodiments there is provided thedocking station capability of FIG. 7 for primary VSCU units, but nodocking station capability for auxiliary VSCU units, wherein auxiliaryVSCU units are simply provided in monolithic form as dedicated auxiliarytabletop VSCU units, dedicated auxiliary wall-mounted VSCU units, and soforth. One advantage of providing an auxiliary VSCU unit, such as atabletop VSCU unit, without a docking functionality would be itssimplicity and non-intimidating nature for users, since the user wouldsimply be required to place it on a table (their nightstand, forexample) and just plug it in, just as easily as they would a clockradio.

In still other embodiments, all VSCU units are provided as non-dockingtypes, but are interchangeable in their abilities as primary andauxiliary VSCU units. In still other embodiments, all VSCU units areprovided as non-docking types and are non-interchangeable in theirprimary versus auxiliary abilities, that is, there is a first set ofVSCU units that can only serve as primary VSCU units and a second set ofVSCU units that can only serve as auxiliary VSCU units. For embodimentsin which primary VSCU units are provided as non-docking types, theirphysical architecture may still be separable into two components for thepurpose of streamlining the installation process, with one componentbeing similar to the HVAC-coupling wall dock 702 of FIG. 7 and thesecond component being the main unit as shown in FIG. 7, except that theassembly is not intended for docking-style user separability afterinstallation is complete. For convenience of description hereinbelow andso as not to unnecessarily limit the scope of the present teachings, theclassification of one or more described VSCU units as being of (i) anon-docking type versus a docking type, and/or (ii) a primary typeversus an auxiliary type, may not be specified, in which case VSCU unitsof any of these classifications may be used with such embodiments, or inwhich case such classification will readily inferable by the skilledartisan from the context of the description.

FIG. 8A illustrates a conceptual diagram of an HVAC-coupling wall dock702′ with particular reference to a set of input wiring ports 851thereof, and which represents a first version of the HVAC-coupling walldock 702 of FIG. 7 that is manufactured and sold in a “simple” or “DIY(do-it-yourself)” product package in conjunction with the VSCU unit 700.The input wiring ports 851 of the HVAC-coupling wall dock 702′ arejudiciously limited in number and selection to represent a business andtechnical compromise between (i) providing enough control signal inputsto meet the needs of a reasonably large number of HVAC systems in areasonably large number of households, while also (ii) not intimidatingor overwhelming the do-it-yourself customer with an overly complex arrayof connection points. For one embodiment, the judicious selection ofinput wiring ports 851 consists of the following set: Rh (24 VAC heatingcall switch power); Rc (24VAC cooling call switch power); W (heatingcall); Y (cooling call); G (fan); and O/B (heat pump).

The HVAC-coupling wall dock 702′ is configured and designed inconjunction with the VSCU unit 700, including both hardware aspects andprogramming aspects, to provide a DIY installation process that issimple, non-intimidating, and perhaps even fun for many DIY installers,and that further provides an appreciable degree of foolproofingcapability for protecting the HVAC system from damage and for ensuringthat the correct signals are going to the correct equipment. For oneembodiment, the HVAC-coupling wall dock 702′ is equipped with a smallmechanical detection switch (not shown) for each distinct input port,such that the insertion of a wire (and, of course, the non-insertion ofa wire) is automatically detected and a corresponding indication signalis provided to the VSCU 100 upon initial docking. In this way, the VSCU100 has knowledge for each individual input port whether a wire has, orhas not been, inserted into that port. Preferably, the VSCU unit 700 isalso provided with electrical sensors (e.g., voltmeter, ammeter, andohmmeter) corresponding to each of the input wiring ports 851. The VSCU100 is thereby enabled, by suitable programming, to perform somefundamental “sanity checks” at initial installation. By way of example,if there is no input wire at either the Rc or Rh terminal, or if thereis no AC voltage sensed at either of these terminals, furtherinitialization activity can be immediately halted, and the user notifiedon the circular display monitor 102, because there is either no power atall or the user has inserted the Rc and/or Rh wires into the wrongterminal. By way of further example, if there is alive voltage on theorder of 24 VAC detected at any of the W, Y, and G terminals, then itcan be concluded that the user has placed the Rc and/or Rh wire in thewrong place, and appropriate installation halting and user notificationcan be made.

One particularly advantageous feature from a safety and equipmentpreservation perspective provided according to one embodiment relates toautomated opening versus automated shunting of the Rc and Rh terminalsby the VSCU unit 700. In many common home installations, instead ofthere being separate wires provided for Rc (24 VAC heating call switchpower) and Rh (24 VAC cooling call switch power), there is only a single24VAC call switch power lead provided. This single 24VAC lead, whichmight be labeled R, V, Rh, or Rc depending on the unique history andgeographical location of the home, provides the call switch power forboth heating and cooling. For such cases, it is electrically necessaryfor any thermostat to have its Rc and Rh input ports shunted together sothat the power from that single lead can be respectively accessed by theheating and cooling call switches. However, in many other common homeinstallations, there are separate 24 VAC wires provided for Rc and Rhrunning from separate transformers and, when so provided, it isimportant not to shunt them together to avoid equipment damage. Thesesituations are resolved historically by (i) the professional installerexamining the HVAC system and ensuring that a shunting lead (orequivalent DIP switch setting) is properly installed or not installed asappropriate, and/or (ii) the historical presence on most thermostats ofa discrete user-toggled mechanical or electromechanical switch (e.g.,HEAT-OFF-COOL) to ensure that heating and cooling are neversimultaneously activated. Notably, it is desired to omit any discretemechanical HEAT-OFF-COOL in most embodiments and to eliminate the needfor a professional installer for the instant DIY product versionenvironment. Advantageously, according to an embodiment, the VSCU 100 isadvantageously equipped and programmed to (i) automatically test theinserted wiring to classify the user's HVAC system into one of the abovetwo types (i.e., single call power lead versus dual call power leads),(ii) to automatically ensure that the Rc and Rh input ports remainelectrically segregated if the if the user's HVAC system is determinedto be of the dual call power lead type, and (iii) to automatically shuntthe Rc and Rh input ports together if the user's HVAC system isdetermined to be of the single call power lead type. The automatictesting can comprise, without limitation, electrical sensing such asthat provided by voltmeter, ammeters, ohmmeters, and reactance-sensingcircuitry, as well as functional detection as described further below.

Also provided at installation time according to an embodiment, which isparticularly useful and advantageous in the DIY scenario, is automatedfunctional testing of the HVAC system by the VSCU unit 700 based on thewiring insertions made by the installer as detected by the smallmechanical detection switches at each distinct input port. Thus, forexample, where an insertion into the W (heating call) input port ismechanically sensed at initial startup, the VSCU unit 700 actuates thefurnace (by coupling W to Rh) and then automatically monitors thetemperature over a predetermined period, such as ten minutes. If thetemperature is found to be rising over that predetermined period, thenit is determined that the W (heating call) lead has been properlyconnected to the W (heating call) input port. However, if thetemperature is found to be falling over that predetermined period, thenit is determined that Y (cooling call) lead has likely been erroneouslyconnected to the W (heating call) input port. For one embodiment, whensuch error is detected, the system is shut down and the user is notifiedand advised of the error on the circular display monitor 102. Foranother embodiment, when such error is detected, the VSCU unit 700automatically reassigns the W (heating call) input port as a Y (coolingcall) input port to automatically correct the error. Similarly,according to an embodiment, where the Y (cooling call) lead ismechanically sensed at initial startup, the VSCU unit 700 actuates theair conditioner (by coupling Y to Rc) and then automatically monitorsthe temperature, validating the Y connection if the temperature issensed to be falling and invalidating the Y connection (and, optionally,automatically correcting the error by reassigning the Y input port as aW input port) if the temperature is sensed to be rising. In view of thepresent disclosure, the determination and incorporation of otherautomated functional tests into the above-described method for otherHVAC functionality would be achievable by the skilled artisan and arewithin the scope of the present teachings. By way of example, for oneembodiment there can be a statistical study done on the electrical noisepatterns associated with the different control wires and a unique orpartially unique “noise fingerprint” associated with the differentwires, and then the VSCU unit 700 can automatically sense the noise oneach of the existing control wires to assist in the automated testingand verification process.

Also provided at installation time according to an embodiment, which islikewise particularly advantageous in the DIY scenario, is automateddetermination of the homeowner's pre-existing heat pump wiringconvention when an insertion onto the O/B (heat pump) input port ismechanically sensed at initial startup. Depending on a combination ofseveral factors such as the history of the home, the geographical regionof the home, and the particular manufacturer and installation year ofthe home's heat pump, there may be a different heat pump signalconvention used with respect to the direction of operation (heating orcooling) of the heat pump. According to an embodiment, the VSCU unit 700automatically and systematically applies, for each of a plurality ofpreselected candidate heat pump actuation signal conventions, a coolingactuation command and a heating actuation command, each actuationcommand being followed by a predetermined time period over which thetemperature change is sensed. If the cooling command according to thepresently selected candidate convention is followed by a sensed periodof falling temperature, and the heating command according to thepresently selected candidate convention is followed by a sensed periodof rising temperature, then the presently selected candidate conventionis determined to be the actual heat pump signal convention for thathome. If, on the other hand, the cooling command was not followed by asensed period of cooling and/or the heating command was not followed bya sensed period of heating, then the presently selected candidateconvention is discarded and the VSCU unit 700 repeats the process forthe next candidate heat pump actuation signal convention. For oneexample, a first candidate heat pump actuation signal convention is (a)for cooling, leave O/B open and connect Y to Rc, and (b) for heating,connect O/B to Rh, while a second candidate heat pump actuation signalconvention is (a) for cooling, connect O/B to Rc, and (b) for heating,leave O/B open and connect W to Rh. In view of the present disclosure,the determination and incorporation of other candidate heat pumpactuation signal conventions into the above-described method would beachievable by the skilled artisan and are within the scope of thepresent teachings.

FIG. 8B illustrates a conceptual diagram of an HVAC-coupling wall dock702″ with particular reference to a set of input wiring ports 861thereof, and which represents a second version of the HVAC-coupling walldock 702 of FIG. 7 that is manufactured and sold in a “professional”product package in conjunction with the VSCU unit 700. The professionalproduct package is preferably manufactured and marketed withprofessional installation in mind, such as by direct marketing to HVACservice companies, general contractors involved in the construction ofnew homes, or to homeowners having more complex HVAC systems with arecommendation for professional installation. The input wiring ports 861of the HVAC-coupling wall dock 702″ are selected to be sufficient toaccommodate both simple and complex HVAC systems alike. For oneembodiment, the input wiring ports 861 include the following set: Rh (24VAC heating call switch power); Rc (24VAC cooling call switch power); W1(first stage heating call); W2 (second stage heating call); Y1 (firststage cooling call); Y2 (second stage cooling call); G (fan); O/B (heatpump); AUX (auxiliary device call); E (emergency heating call); HUM(humidifier call); and DEHUM (dehumidifier call). For one embodiment,even though professional installation is contemplated, the HVAC-couplingwall dock 702″ is nevertheless provided with small mechanical detectionswitches (not shown) at the respective input wiring ports for wireinsertion sensing, and the VSCU unit 700 is provided with one or more ofthe various automated testing and automated configuration capabilitiesassociated with the DIY package described above, which may be useful forsome professional installers and/or more technically savvydo-it-yourselfers confident enough to perform the professional-modelinstallation for their more advanced HVAC systems.

FIGS. 9A-9B illustrate a thermostat 900 having a user-friendlyinterface, according to some embodiments. The term “thermostat” is usedhereinbelow to represent a particular type of VSCU unit (VersatileSensing and Control) that is particularly applicable for HVAC control inan enclosure. Although “thermostat” and “VSCU unit” may be seen asgenerally interchangeable for the contexts of HVAC control of anenclosure, it is within the scope of the present teachings for each ofthe embodiments hereinabove and hereinbelow to be applied to VSCU unitshaving control functionality over measurable characteristics other thantemperature (e.g., pressure, flow rate, height, position, velocity,acceleration, capacity, power, loudness, brightness) for any of avariety of different control systems involving the governance of one ormore measurable characteristics of one or more physical systems, and/orthe governance of other energy or resource consuming systems such aswater usage systems, air usage systems, systems involving the usage ofother natural resources, and systems involving the usage of variousother forms of energy. Unlike many prior art thermostats, thermostat 900preferably has a sleek, simple, uncluttered and elegant design that doesnot detract from home decoration, and indeed can serve as a visuallypleasing centerpiece for the immediate location in which it isinstalled. Moreover, user interaction with thermostat 900 is facilitatedand greatly enhanced over known conventional thermostats by the designof thermostat 900. The thermostat 900 includes control circuitry and iselectrically connected to an HVAC system, such as is shown withthermostat 110 in FIGS. 1 and 2. Thermostat 900 is wall mounted, iscircular in shape, and has an outer rotatable ring 912 for receivinguser input. Thermostat 900 is circular in shape in that it appears as agenerally disk-like circular object when mounted on the wall. Thermostat900 has a large front face lying inside the outer ring 912. According tosome embodiments, thermostat 900 is approximately 80 mm in diameter. Theouter rotatable ring 912 allows the user to make adjustments, such asselecting a new target temperature. For example, by rotating the outerring 912 clockwise, the target temperature can be increased, and byrotating the outer ring 912 counter-clockwise, the target temperaturecan be decreased. The front face of the thermostat 900 comprises a clearcover 914 that according to some embodiments is polycarbonate, and ametallic portion 924 preferably having a number of slots formed thereinas shown. According to some embodiments, the surface of cover 914 andmetallic portion 924 form a common outward arc or spherical shape gentlyarcing outward, and this gentle arcing shape is continued by the outerring 912.

Although being formed from a single lens-like piece of material such aspolycarbonate, the cover 914 has two different regions or portionsincluding an outer portion 914 o and a central portion 914 i. Accordingto some embodiments, the cover 914 is painted or smoked around the outerportion 914 o, but leaves the central portion 914 i visibly clear so asto facilitate viewing of an electronic display 916 disposedthereunderneath. According to some embodiments, the curved cover 914acts as a lens that tends to magnify the information being displayed inelectronic display 916 to users. According to some embodiments thecentral electronic display 916 is a dot-matrix layout (individuallyaddressable) such that arbitrary shapes can be generated, rather thanbeing a segmented layout. According to some embodiments, a combinationof dot-matrix layout and segmented layout is employed. According to someembodiments, central display 916 is a backlit color liquid crystaldisplay (LCD). An example of information displayed on the electronicdisplay 916 is illustrated in FIG. 9A, and includes central numerals 920that are representative of a current setpoint temperature. According tosome embodiments, metallic portion 924 has number of slot-like openingsso as to facilitate the use of a passive infrared motion sensor 930mounted therebeneath. The metallic portion 924 can alternatively betermed a metallic front grille portion. Further description of themetallic portion/front grille portion is provided in the commonlyassigned U.S. Ser. No. 13/199,108, supra. The thermostat 900 ispreferably constructed such that the electronic display 916 is at afixed orientation and does not rotate with the outer ring 912, so thatthe electronic display 916 remains easily read by the user. For someembodiments, the cover 914 and metallic portion 924 also remain at afixed orientation and do not rotate with the outer ring 912. Accordingto one embodiment in which the diameter of the thermostat 900 is about80 mm, the diameter of the electronic display 916 is about 45 mm.According to some embodiments an LED indicator 980 is positioned beneathportion 924 to act as a low-power-consuming indicator of certain statusconditions. For, example the LED indicator 980 can be used to displayblinking red when a rechargeable battery of the thermostat (see FIG. 4A,infra) is very low and is being recharged. More generally, the LEDindicator 980 can be used for communicating one or more status codes orerror codes by virtue of red color, green color, various combinations ofred and green, various different blinking rates, and so forth, which canbe useful for troubleshooting purposes.

Motion sensing as well as other techniques can be use used in thedetection and/or predict of occupancy, as is described further in thecommonly assigned U.S. Ser. No. 12/881,430, supra. According to someembodiments, occupancy information is used in generating an effectiveand efficient scheduled program. Preferably, an active proximity sensor970A is provided to detect an approaching user by infrared lightreflection, and an ambient light sensor 970B is provided to sensevisible light. The proximity sensor 970A can be used to detect proximityin the range of about one meter so that the thermostat 900 can initiate“waking up” when the user is approaching the thermostat and prior to theuser touching the thermostat. Such use of proximity sensing is usefulfor enhancing the user experience by being “ready” for interaction assoon as, or very soon after the user is ready to interact with thethermostat. Further, the wake-up-on-proximity functionality also allowsfor energy savings within the thermostat by “sleeping” when no userinteraction is taking place our about to take place. The ambient lightsensor 970B can be used for a variety of intelligence-gatheringpurposes, such as for facilitating confirmation of occupancy when sharprising or falling edges are detected (because it is likely that thereare occupants who are turning the lights on and off), and such as fordetecting long term (e.g., 24-hour) patterns of ambient light intensityfor confirming and/or automatically establishing the time of day.

According to some embodiments, for the combined purposes of inspiringuser confidence and further promoting visual and functional elegance,the thermostat 900 is controlled by only two types of user input, thefirst being a rotation of the outer ring 912 as shown in FIG. 99A(referenced hereafter as a “rotate ring” or “ring rotation” input), andthe second being an inward push on an outer cap 908 (see FIG. 9B) untilan audible and/or tactile “click” occurs (referenced hereafter as an“inward click” or simply “click” input). For the embodiment of FIGS.9A-9B, the outer cap 908 is an assembly that includes all of the outerring 912, cover 914, electronic display 916, and metallic portion 924.When pressed inwardly by the user, the outer cap 908 travels inwardly bya small amount, such as 0.5 mm, against an interior metallic dome switch(not shown), and then springably travels back outwardly by that sameamount when the inward pressure is released, providing a satisfyingtactile “click” sensation to the user's hand, along with a correspondinggentle audible clicking sound. Thus, for the embodiment of FIGS. 9A-9B,an inward click can be achieved by direct pressing on the outer ring 912itself, or by indirect pressing of the outer ring by virtue of providinginward pressure on the cover 914, metallic portion 914, or by variouscombinations thereof. For other embodiments, the thermostat 900 can bemechanically configured such that only the outer ring 912 travelsinwardly for the inward click input, while the cover 914 and metallicportion 924 remain motionless. It is to be appreciated that a variety ofdifferent selections and combinations of the particular mechanicalelements that will travel inwardly to achieve the “inward click” inputare within the scope of the present teachings, whether it be the outerring 912 itself, some part of the cover 914, or some combinationthereof. However, it has been found particularly advantageous to providethe user with an ability to quickly go back and forth betweenregistering “ring rotations” and “inward clicks” with a single hand andwith minimal amount of time and effort involved, and so the ability toprovide an inward click directly by pressing the outer ring 912 has beenfound particularly advantageous, since the user's fingers do not need tobe lifted out of contact with the device, or slid along its surface, inorder to go between ring rotations and inward clicks. Moreover, byvirtue of the strategic placement of the electronic display 916centrally inside the rotatable ring 912, a further advantage is providedin that the user can naturally focus their attention on the electronicdisplay throughout the input process, right in the middle of where theirhand is performing its functions. The combination of intuitive outerring rotation, especially as applied to (but not limited to) thechanging of a thermostat's setpoint temperature, conveniently foldedtogether with the satisfying physical sensation of inward clicking,together with accommodating natural focus on the electronic display inthe central midst of their fingers' activity, adds significantly to anintuitive, seamless, and downright fun user experience. Furtherdescriptions of advantageous mechanical user-interfaces and relateddesigns, which are employed according to some embodiments, can be foundin U.S. Ser. No. 13/033,573, supra, U.S. Ser. No. 29/386,021, supra, andU.S. Ser. No. 13/199,108, supra.

FIG. 9C illustrates a cross-sectional view of a shell portion 909 of aframe of the thermostat of FIGS. 9A-B, which has been found to provide aparticularly pleasing and adaptable visual appearance of the overallthermostat 900 when viewed against a variety of different wall colorsand wall textures in a variety of different home environments and homesettings. While the thermostat itself will functionally adapt to theuser's schedule as described herein and in one or more of the commonlyassigned incorporated applications, supra, the outer shell portion 909is specially configured to convey a “chameleon” quality orcharacteristic such that the overall device appears to naturally blendin, in a visual and decorative sense, with many of the most common wallcolors and wall textures found in home and business environments, atleast in part because it will appear to assume the surrounding colorsand even textures when viewed from many different angles. The shellportion 909 has the shape of a frustum that is gently curved when viewedin cross-section, and comprises a sidewall 976 that is made of a clearsolid material, such as polycarbonate plastic. The sidewall 976 isbackpainted with a substantially flat silver- or nickel-colored paint,the paint being applied to an inside surface 978 of the sidewall 976 butnot to an outside surface 977 thereof. The outside surface 977 is smoothand glossy but is not painted. The sidewall 976 can have a thickness Tof about 1.5 mm, a diameter d1 of about 78.8 mm at a first end that isnearer to the wall when mounted, and a diameter d2 of about 81.2 mm at asecond end that is farther from the wall when mounted, the diameterchange taking place across an outward width dimension “h” of about 22.5mm, the diameter change taking place in either a linear fashion or, morepreferably, a slightly nonlinear fashion with increasing outwarddistance to form a slightly curved shape when viewed in profile, asshown in FIG. 9C. The outer ring 912 of outer cap 908 is preferablyconstructed to match the diameter d2 where disposed near the second endof the shell portion 909 across a modestly sized gap gltherefrom, andthen to gently arc back inwardly to meet the cover 914 across a smallgap g2. It is to be appreciated, of course, that FIG. 9C onlyillustrates the outer shell portion 909 of the thermostat 900, and thatthere are many electronic components internal thereto that are omittedfrom FIG. 9C for clarity of presentation, such electronic componentsbeing described further hereinbelow and/or in other ones of the commonlyassigned incorporated applications, such as U.S. Ser. No. 13/199,108,supra.

According to some embodiments, the thermostat 900 includes a processingsystem 960, display driver 964 and a wireless communications system 966.The processing system 960 is adapted to cause the display driver 964 anddisplay area 916 to display information to the user, and to receiveruser input via the rotatable ring 912. The processing system 960,according to some embodiments, is capable of carrying out the governanceof the operation of thermostat 900 including the user interface featuresdescribed herein. The processing system 960 is further programmed andconfigured to carry out other operations as described furtherhereinbelow and/or in other ones of the commonly assigned incorporatedapplications. For example, processing system 960 is further programmedand configured to maintain and update a thermodynamic model for theenclosure in which the HVAC system is installed, such as described inU.S. Ser. No. 12/881,463, supra. According to some embodiments, thewireless communications system 966 is used to communicate with devicessuch as personal computers and/or other thermostats or HVAC systemcomponents, which can be peer-to-peer communications, communicationsthrough one or more servers located on a private network, or and/orcommunications through a cloud-based service.

FIGS. 10A-10B illustrate exploded front and rear perspective views,respectively, of the thermostat 900 with respect to its two maincomponents, which are the head unit 1100 and the back plate 1300.Further technical and/or functional descriptions of various ones of theelectrical and mechanical components illustrated herein below can befound in one or more of the commonly assigned incorporated applications,such as U.S. Ser. No. 13/199,108, supra. In the drawings shown, the “z”direction is outward from the wall, the “y” direction is the head-to-toedirection relative to a walk-up user, and the “x” direction is theuser's left-to-right direction.

FIGS. 11A-11B illustrate exploded front and rear perspective views,respectively, of the head unit 1100 with respect to its primarycomponents. Head unit 1100 includes a head unit frame 1110, the outerring 1120 (which is manipulated for ring rotations), a head unit frontalassembly 1130, a front lens 1180, and a front grille 1190. Electricalcomponents on the head unit frontal assembly 1130 can connect toelectrical components on the backplate 1300 by virtue of ribbon cablesand/or other plug type electrical connectors.

FIGS. 12A-12B illustrate exploded front and rear perspective views,respectively, of the head unit frontal assembly 1130 with respect to itsprimary components. Head unit frontal assembly 1130 comprises a headunit circuit board 1140, a head unit front plate 1150, and an LCD module1160. The components of the front side of head unit circuit board 1140are hidden behind an RF shield in FIG. 12A but are discussed in moredetail below with respect to FIG. 15. On the back of the head unitcircuit board 1140 is a rechargeable Lithium-Ion battery 1144, which forone preferred embodiment has a nominal voltage of 3.7 volts and anominal capacity of 560 mAh. To extend battery life, however, thebattery 1144 is normally not charged beyond 450 mAh by the thermostatbattery charging circuitry. Moreover, although the battery 1144 is ratedto be capable of being charged to 4.2 volts, the thermostat batterycharging circuitry normally does not charge it beyond 3.95 volts. Alsovisible in FIG. 21B is an optical finger navigation module 1142 that isconfigured and positioned to sense rotation of the outer ring 1120. Themodule 1142 uses methods analogous to the operation of optical computermice to sense the movement of a texturable surface on a facing peripheryof the outer ring 1120. Notably, the module 1142 is one of the very fewsensors that is controlled by the relatively power-intensive head unitmicroprocessor rather than the relatively low-power backplatemicroprocessor. This is achievable without excessive power drainimplications because the head unit microprocessor will invariably beawake already when the user is manually turning the dial, so there is noexcessive wake-up power drain anyway. Advantageously, very fast responsecan also be provided by the head unit microprocessor. Also visible inFIG. 21A is a Fresnel lens 1157 that operates in conjunction with a PIRmotion sensor disposes thereunderneath.

FIGS. 13A-13B illustrate exploded front and rear perspective views,respectively, of the backplate unit 1300 with respect to its primarycomponents. Backplate unit 1300 comprises a backplate rear plate 1310, abackplate circuit board 1320, and a backplate cover 1380. Visible inFIG. 22A are the HVAC wire connectors 1322 that include integrated wireinsertion sensing circuitry, and two relatively large capacitors 1324that are used by part of the power stealing circuitry that is mounted onthe back side of the backplate circuit board 1320 and discussed furtherbelow with respect to FIG. 25.

FIG. 14 illustrates a perspective view of a partially assembled headunit front 1100 showing the positioning of grille member 1190 designedin accordance with aspects of the present invention with respect toseveral sensors used by the thermostat. In some implementations, asdescribed further in U.S. Ser. No. 13/119,108, supra, placement ofgrille member 990 over the Fresnel lens 1157 and an associated PIRmotion sensor 334 conceals and protects these PIR sensing elements,while horizontal slots in the grille member 1190 allow the PIR motionsensing hardware, despite being concealed, to detect the lateral motionof occupants in a room or area. A temperature sensor 330 uses a pair ofthermal sensors to more accurately measure ambient temperature. A firstor upper thermal sensor 330 a associated with temperature sensor 330tends to gather temperature data closer to the area outside or on theexterior of the thermostat while a second or lower thermal sensor 330 btends to collect temperature data more closely associated with theinterior of the housing. In one implementation, each of the temperaturesensors 330 a and 330 b comprises a Texas Instruments TMP112 digitaltemperature sensor chip, while the PIR motion sensor 334 comprisesPerkinElmer DigiPyro PYD 1198 dual element pyrodetector.

To more accurately determine the ambient temperature, the temperaturetaken from the lower thermal sensor 330 b is taken into consideration inview of the temperatures measured by the upper thermal sensor 330 a andwhen determining the effective ambient temperature. This configurationcan advantageously be used to compensate for the effects of internalheat produced in the thermostat by the microprocessor(s) and/or otherelectronic components therein, thereby obviating or minimizingtemperature measurement errors that might otherwise be suffered. In someimplementations, the accuracy of the ambient temperature measurement maybe further enhanced by thermally coupling upper thermal sensor 330 a oftemperature sensor 330 to grille member 1190 as the upper thermal sensor330 a better reflects the ambient temperature than lower thermal sensor334 b. Details on using a pair of thermal sensors to determine aneffective ambient temperature is disclosed in U.S. Pat. No. 4,741,476,which is incorporated by reference herein.

FIG. 15 illustrates a head-on view of the head unit circuit board 1140,which comprises a head unit microprocessor 1502 (such as a TexasInstruments AM3703 chip) and an associated oscillator 1504, along withDDR SDRAM memory 1506, and mass NAND storage 1508. For Wi-Fi capability,there is provided in a separate compartment of RF shielding 1534 a Wi-Fimodule 1510, such as a Murata Wireless Solutions LBWA19XSLZ module,which is based on a Texas Instruments WL1270 chipset supporting the802.11b/g/n WLAN standard. For the Wi-Fi module 1510 there is providedsupporting circuitry 1512 including an oscillator 1514. For ZigBeecapability, there is provided also in a separately shielded RFcompartment a ZigBee module 1516, which can be, for example, a C2530F256module from Texas Instruments. For the ZigBee module 1516 there isprovided supporting circuitry 1518 including an oscillator 1519 and alow-noise amplifier 1520. Also provided is display backlight voltageconversion circuitry 1522, piezoelectric driving circuitry 1524, andpower management circuitry 1526 (local power rails, etc.). Provided on aflex circuit 1528 that attaches to the back of the head unit circuitboard by a flex circuit connector 1530 is a proximity and ambient lightsensor (PROX/ALS), more particularly a Silicon Labs SI1142Proximity/Ambient Light Sensor with an I2C Interface. Also provided arebattery charging-supervision-disconnect circuitry 1532, and spring/RFantennas 1536. Also provided is a temperature sensor 1538 (risingperpendicular to the circuit board in the +z direction containing twoseparate temperature sensing elements at different distances from thecircuit board), and a PIR motion sensor 1540. Notably, even though thePROX/ALS and temperature sensors 1538 and PIR motion sensor 1540 arephysically located on the head unit circuit board 1140, all thesesensors are polled and controlled by the low-power backplatemicrocontroller on the backplate circuit board, to which they areelectrically connected.

FIG. 16 illustrates a rear view of the backplate circuit board 1320,comprising a backplate processor/microcontroller 1602, such as a TexasInstruments MSP430F System-on-Chip Microcontroller that includes anon-board memory 1603. The backplate circuit board 1320 further comprisespower supply circuitry 1604, which includes power-stealing circuitry,and switch circuitry 1606 for each HVAC respective HVAC function. Foreach such function the switch circuitry 1606 includes an isolationtransformer 1608 and a back-to-back NFET package 1610. The use of FETsin the switching circuitry allows for “active power stealing”, i.e.,taking power during the HVAC “ON” cycle, by briefly diverting power fromthe HVAC relay circuit to the reservoir capacitors for a very smallinterval, such as 100 micro-seconds. This time is small enough not totrip the HVAC relay into the “off” state but is sufficient to charge upthe reservoir capacitors. The use of FETs allows for this fast switchingtime (100 micro-seconds), which would be difficult to achieve usingrelays (which stay on for tens of milliseconds). Also, such relays wouldreadily degrade doing this kind of fast switching, and they would alsomake audible noise too. In contrast, the FETS operate with essentiallyno audible noise. Also provided is a combined temperature/humiditysensor module 1612, such as a Sensirion SHT21 module. The backplatemicrocontroller 1602 performs polling of the various sensors, sensingfor mechanical wire insertion at installation, alerting the head unitregarding current vs. setpoint temperature conditions and actuating theswitches accordingly, and other functions such as looking forappropriate signal on the inserted wire at installation.

In accordance with the teachings of the commonly assigned U.S. Ser. No.13/269,501, supra, the commonly assigned U.S. Ser. No. 13/275,307,supra, and others of the commonly assigned incorporated applications,the thermostat 900 represents an advanced, multi-sensing,microprocessor-controlled intelligent or “learning” thermostat thatprovides a rich combination of processing capabilities, intuitive andvisually pleasing user interfaces, network connectivity, andenergy-saving capabilities (including the presently describedauto-away/auto-arrival algorithms) while at the same time not requiringa so-called “C-wire” from the HVAC system or line power from a householdwall plug, even though such advanced functionalities can require agreater instantaneous power draw than a “power-stealing” option (i.e.,extracting smaller amounts of electrical power from one or more HVACcall relays) can safely provide. By way of example, the head unitmicroprocessor 1502 can draw on the order of 250 mW when awake andprocessing, the LCD module 1160 can draw on the order of 250 mW whenactive. Moreover, the Wi-Fi module 1510 can draw 250 mW when active, andneeds to be active on a consistent basis such as at a consistent 2% dutycycle in common scenarios. However, in order to avoid falsely trippingthe HVAC relays for a large number of commercially used HVAC systems,power-stealing circuitry is often limited to power providing capacitieson the order of 100 mW-200 mW, which would not be enough to supply theneeded power for many common scenarios.

The thermostat 900 resolves such issues at least by virtue of the use ofthe rechargeable battery 1144 (or equivalently capable onboard powerstorage medium) that will recharge during time intervals in which thehardware power usage is less than what power stealing can safelyprovide, and that will discharge to provide the needed extra electricalpower during time intervals in which the hardware power usage is greaterthan what power stealing can safely provide. In order to operate in abattery-conscious manner that promotes reduced power usage and extendedservice life of the rechargeable battery, the thermostat 900 is providedwith both (i) a relatively powerful and relatively power-intensive firstprocessor (such as a Texas Instruments AM3703 microprocessor) that iscapable of quickly performing more complex functions such as driving avisually pleasing user interface display and performing variousmathematical learning computations, and (ii) a relatively less powerfuland less power-intensive second processor (such as a Texas InstrumentsMSP430 microcontroller) for performing less intensive tasks, includingdriving and controlling the occupancy sensors. To conserve valuablepower, the first processor is maintained in a “sleep” state for extendedperiods of time and is “woken up” only for occasions in which itscapabilities are needed, whereas the second processor is kept on more orless continuously (although preferably slowing down or disabling certaininternal clocks for brief periodic intervals to conserve power) toperform its relatively low-power tasks. The first and second processorsare mutually configured such that the second processor can “wake” thefirst processor on the occurrence of certain events, which can be termed“wake-on” facilities. These wake-on facilities can be turned on andturned off as part of different functional and/or power-saving goals tobe achieved. For example, a “wake-on-PROX” facility can be provided bywhich the second processor, when detecting a user's hand approaching thethermostat dial by virtue of an active proximity sensor (PROX, such asprovided by a Silicon Labs SI1142 Proximity/Ambient Light Sensor withI2C Interface), will “wake up” the first processor so that it canprovide a visual display to the approaching user and be ready to respondmore rapidly when their hand touches the dial. As another example, a“wake-on-PIR” facility can be provided by which the second processorwill wake up the first processor when detecting motion somewhere in thegeneral vicinity of the thermostat by virtue of a passive infraredmotion sensor (PIR, such as provided by a PerkinElmer DigiPyro PYD 1198dual element pyrodetector). Notably, wake-on-PIR is not synonymous withauto-arrival, as there would need to be N consecutive buckets of sensedPIR activity to invoke auto-arrival, whereas only a single sufficientmotion event can trigger a wake-on-PIR wake-up.

FIGS. 17A-17C illustrate conceptual examples of the sleep-wake timingdynamic, at progressively larger time scales, that can be achievedbetween the head unit (HU) microprocessor and the backplate (BP)microcontroller that advantageously provides a good balance betweenperformance, responsiveness, intelligence, and power usage. The higherplot value for each represents a “wake” state (or an equivalent higherpower state) and the lower plot value for each represents a “sleep”state (or an equivalent lower power state). As illustrated, thebackplate microcontroller is active much more often for polling thesensors and similar relatively low-power tasks, whereas the head unitmicroprocessor stays asleep much more often, being woken up for“important” occasions such as user interfacing, network communication,and learning algorithm computation, and so forth. A variety of differentstrategies for optimizing sleep versus wake scenarios can be achieved bythe disclosed architecture and is within the scope of the presentteachings. For example, the commonly assigned U.S. Ser. No. 13/275,307,supra, describes a strategy for conserving head unit microprocessor“wake” time while still maintaining effective and timely communicationswith a cloud-based thermostat management server via the thermostat'sWi-Fi facility.

FIG. 18 illustrates a self-descriptive overview of the functionalsoftware, firmware, and/or programming architecture of the head unitmicroprocessor for achieving its described functionalities. FIG. 19illustrates a self-descriptive overview of the functional software,firmware, and/or programming architecture of the backplatemicrocontroller for achieving its described functionalities.

FIG. 20 illustrates a thermostat 2000 according to a preferredembodiment, the thermostat 2000 comprising selected feature combinationsthat have been found to be particularly advantageous for thefacilitation of do-it-yourself thermostat installation, theaccommodation of a variety of different practical installation scenarios(including scenarios where a “C” power wire is not available), theprovisioning of relatively power-intensive advanced interfaces andfunctionalities (e.g., a large visually pleasing electronic display, arelatively powerful general purpose microprocessor, and a reliable Wi-Ficommunications chip) even where a “C” power wire is not available, thefacilitation of operational robustness and durability, compact devicesize, quietness of operation, and other advantageous characteristicsdescribed in the instant disclosure and/or the commonly assignedincorporated applications. In the discussion that follows, the followingHVAC wiring shorthand notations are used: W (heat call relay wire); Y(cooling call relay wire); Rh (heat call relay power); Rc (cooling callrelay power); G (fan call relay wire); O/B (heat pump call relay wire);AUX (auxiliary call relay wire); and C (common wire).

The Rh wire, which leads to one side of the HVAC power transformer (orsimply “HVAC transformer”) that is associated with a heating call relay,can go by different names in the art, which can include heating callswitch power wire, heat call power return wire, heat return wire, returnwire for heating, or return for heating. The Rc wire, which leads to oneside of the HVAC transformer that is associated with a cooling callrelay, can likewise go by different names including cooling call switchpower wire, cooling call power return wire, cooling return wire, returnwire for cooling, or return for cooling. In the case ofsingle-HVAC-transformer systems having both heating and coolingfunctions, it is one and the same HVAC power transformer that isassociated with both the heating call relay and cooling call relay, andin such cases there is just a single wire, usually labeled “R”, leadingback to one side of that HVAC transformer, which likewise can go bydifferent names in the art including call switch power wire, call relaypower wire, call power return wire, power return wire, or simply returnwire.

As illustrated generally in FIG. 20, the thermostat 2000 comprises ahead unit 2002 and a backplate 2004. The backplate 2004 comprises aplurality of FET switches 2006 used for carrying out the essentialthermostat operations of connecting or “shorting” one or more selectedpairs of HVAC wires together according to the desired HVAC operation.The details of FET switches 2006, each of which comprises a dualback-to-back FET configuration, can be found elsewhere in the instantdisclosure and/or in the commonly assigned U.S. Ser. No. 13/034,674,supra. The operation of each of the FET switches 2006 is controlled by abackplate microcontroller 2008 which can comprise, for example, anMSP430 16-bit ultra-low power RISC mixed-signal microprocessor availablefrom Texas Instruments.

Thermostat 2000 further comprises powering circuitry 2010 that comprisescomponents contained on both the backplate 2004 and head unit 2002.Generally speaking, it is the purpose of powering circuitry 2010 toextract electrical operating power from the HVAC wires and convert thatpower into a usable form for the many electrically-driven components ofthe thermostat 2000. Thermostat 2000 further comprises insertion sensingcomponents 2012 configured to provide automated mechanical andelectrical sensing regarding the HVAC wires that are inserted into thethermostat 2000. Thermostat 2000 further comprises a relativelyhigh-power head unit microprocessor 2032, such as an AM3703 Sitara ARMmicroprocessor available from Texas Instruments, that provides the maingeneral governance of the operation of the thermostat 2000. Thermostat2000 further comprises head unit/backplate environmental sensors2034/2038 (e.g., temperature sensors, humidity sensors, active IR motionsensors, passive IR motion sensors, ambient visible light sensors,accelerometers, ambient sound sensors, ultrasonic/infrasonic soundsensors, etc.), as well as other components 2036 (e.g., electronicdisplay devices and circuitry, user interface devices and circuitry,wired communications circuitry, wireless communications circuitry suchas Wi-Fi and/or ZigBee chips) that are operatively coupled to the headunit microprocessor 2032 and/or backplate microprocessor 2008 andcollectively configured to provide the functionalities described in theinstant disclosure and/or the commonly assigned incorporatedapplications.

The insertion sensing components 2012 include a plurality of HVAC wiringconnectors 2014, each containing an internal springable mechanicalassembly that, responsive to the mechanical insertion of a physical wirethereinto, will mechanically cause an opening or closing of one or morededicated electrical switches associated therewith. Exemplaryconfigurations for each of the HVAC wiring connectors 2014 can be foundin the commonly assigned U.S. Ser. No. 13/034,666, supra. With respectto the HVAC wiring connectors 2014 that are dedicated to the C, W, Y,Rc, and Rh terminals, those dedicated electrical switches are, in turn,networked together in a manner that yields the results that areillustrated in FIG. 20 by the blocks 2016 and 2018. For clarity ofpresentation in FIG. 20, the block 2016 is shown as being coupled to theinternal sensing components 2012 by virtue of double lines 2015 termed“mechanical causation,” for the purpose of denoting that the output ofblock 2016 is dictated solely by virtue of the particular combination ofHVAC wiring connectors 2014 into which wires have been mechanicallyinserted. More specifically, the output of block 2016, which is providedat a node 2019, is dictated solely by virtue of the particularcombination of C, W, and Y connectors into which wires have beenmechanically inserted. Still more specifically, the output of block 2016at node 2019 is provided in accordance with the following rules: if awire is inserted into the C connector, then the node 2019 becomes the Cnode regardless of whether there are any wires inserted into the Y or Wconnectors; if no wire is inserted into the C connector and a wire isinserted into the Y connector, then the node 2019 becomes the Y noderegardless of whether there is a wire inserted into the W connector; andif no wire is inserted into either of the C or Y connectors, then thenode 2019 becomes the W node. Exemplary configurations for achieving thefunctionality of block 2016 (as combined with components 2012 and wiringconnectors 2014) can be found elsewhere in the instant disclosure and/orin the commonly assigned U.S. Ser. No. 13/034,678, supra. It is to beappreciated that, although mechanical causation for achieving thefunctionality of block 2016 (as combined with components 2012 and wiringconnectors 2014) has been found to be particularly advantageous forsimplicity and do-it-yourself (“DIY”) foolproofing, in other embodimentsthere can be similar functionalities carried out electrically,magnetically, optically, electro-optically, electro-mechanically, etc.without departing from the scope of the present teachings. Thus, forexample, similar results could be obtained by using optically,electrically, and/or magnetically triggered wire insertion sensingcomponents that are coupled to relays or electronic switches that carryout the functionality of block 2016 (as combined with components 2012and wiring connectors 2014) without departing from the scope of thepresent teachings.

Likewise, for clarity of presentation in FIG. 20, the block 2018 is alsoshown as being coupled to the internal sensing components 2012 by virtueof double lines termed “mechanical causation,” for the purpose ofdenoting that its operation, which is either to short the Rc and Rhnodes together or not to short the Rc and Rh nodes together, is dictatedsolely by virtue of the particular combination of HVAC wiring connectors2014 into which wires have been mechanically inserted. Morespecifically, whether the block 2018 will short, or not short, the Rcand Rh nodes together is dictated solely by virtue of the particularcombination of Rc and Rh connectors into which wires have beenmechanically inserted. Still more specifically, the block 2018 will keepthe Rc and Rh nodes shorted together, unless wires have been insertedinto both the Rc and Rh connectors, in which case the block 2018 willnot short the Rc and Rh nodes together because a two-HVAC-transformersystem is present. Exemplary configurations for achieving thefunctionality of block 2018 (as combined with components 2012 and wiringconnectors 2014) can be found elsewhere in the instant disclosure and/orin the commonly assigned U.S. Ser. No. 13/034,674, supra. It is to beappreciated that, although mechanical causation for achieving thefunctionality of block 2018 (as combined with components 2012 and wiringconnectors 2014) has been found to be particularly advantageous forsimplicity and do-it-yourself (“DIY”) foolproofing, in other embodimentsthere can be similar functionalities carried out electrically,magnetically, optically, electro-optically, electro-mechanically, etc.,in different combinations, without departing from the scope of thepresent teachings. Thus, for example, similar results could be obtainedby using optically, electrically, and/or magnetically triggered wireinsertion sensing components that are coupled to relays or electronicswitches that carry out the functionality of block 2018 (as combinedwith components 2012 and wiring connectors 2014) without departing fromthe scope of the present teachings.

As illustrated in FIG. 20, the insertion sensing circuitry 2012 is alsoconfigured to provide electrical insertion sensing signals 2013 to othercomponents of the thermostat 2000, such as the backplate microcontroller2008. Preferably, for each of the respective HVAC wiring terminal 2014,there is provided at least two signals in electrical form to themicrocontroller 2008, the first being a simple “open” or “short” signalthat corresponds to the mechanical insertion of a wire, and the secondbeing a voltage or other level signal (in analog form or, optionally, indigitized form) that represents a sensed electrical signal at thatterminal (as measured, for example, between that terminal and aninternal thermostat ground node). Exemplary configurations for providingthe sensed voltage signal can be found elsewhere in the instantdisclosure and/or in the commonly assigned U.S. Ser. No. 13/034,674,supra. The first and second electrical signals for each of therespective wiring terminals can advantageously be used as a basis forbasic “sanity checking” to help detect and avoid erroneous wiringconditions. For example, if there has been a wire inserted into the “C”connector, then there should be a corresponding voltage level signalsensed at the “C” terminal, and if that corresponding voltage levelsignal is not present or is too low, then an error condition isindicated because there should always be a voltage coming from one sideof the HVAC power transformer (assuming that HVAC system power is on, ofcourse). As another example, if there has been a wire inserted into the“O/B” connector (heat pump call relay wire) but no wire has beeninserted into the “Y” connector (cooling call relay wire), then an errorcondition is indicated because both of these wires are needed for properheat pump control. Exemplary ways for conveying proper and/or improperwiring status information to the user can be found elsewhere in theinstant disclosure and/or in the commonly assigned U.S. Ser. No.13/269,501, supra.

Basic operation of each of the FET switches 2006 is achieved by virtueof a respective control signal (OFF or ON) provided by the backplatemicrocontroller 2008 that causes the corresponding FET switch 2006 to“connect” or “short” its respective HVAC lead inputs for an ON controlsignal, and that causes the corresponding FET switch 2006 to“disconnect” or “leave open” or “open up” its respective HVAC leadinputs for an OFF control signal. For example, the W-Rh FET switch keepsthe W and Rh leads disconnected from each other unless there is anactive heating call, in which case the W-Rh FET switch shorts the W andRh leads together. As a further example, the Y-Rc FET switch keeps the Yand Rc leads disconnected from each other unless there is an activecooling call, in which case the Y-Rc FET switch shorts the Y and Rcleads together. (There is one exception to this basic operation for theparticular case of “active power stealing” that is discussed in moredetail infra, in which case the FET switch corresponding to the HVAClead from which power is being stolen is opened up for very briefintervals during an active call involving that lead. Thus, ifpower-stealing is being performed using the Y lead, then during anactive cooling call the Y-Rc FET switch is opened up for very briefintervals from time to time, these brief intervals being short enoughsuch that the Y HVAC relay does not un-trip.)

Advantageously, by virtue of the above-described operation of block2018, it is automatically the case that for single-transformer systemshaving only an “R” wire (rather than separate Rc and Rh wires as wouldbe present for two-transformer systems), that “R” wire can be insertedinto either of the Rc or Rh terminals, and the Rh-Rc nodes will beautomatically shorted to form a single “R” node, as needed for properoperation. In contrast, for dual-transformer systems, the insertion oftwo separate wires into the respective Rc and Rh terminals will causethe Rh-Rc nodes to remain disconnected to maintain two separate Rc andRh nodes, as needed for proper operation. The G-Rc FET switch keeps theG and Rc leads disconnected from each other unless there is an activefan call, in which case the G-Rc FET switch shorts the G and Rc leadstogether (and, advantageously, the proper connection will be achievedregardless of whether the there is a single HVAC transformer or dualHVAC transformers because the Rc and Rh terminals will be automaticallyshorted or isolated accordingly). The AUX-Rh FET switch keeps the AUXand Rh leads disconnected from each other unless there is an active AUXcall, in which case the AUX-Rh FET switch shorts the AUX and Rh leadstogether (and, advantageously, the proper connection will be achievedregardless of whether the there is a single HVAC transformer or dualHVAC transformers because the Rc and Rh terminals will be automaticallyshorted or isolated accordingly). For heat pump calls, the O/B-Rc FETswitch and Y-Rc FET switch are jointly operated according to therequired installation-dependent convention for forward or reverseoperation (for cooling or heating, respectively), which convention canadvantageously be determined automatically (or semi-automatically usingfeedback from the user) by the thermostat 2000 as described further inthe commonly assigned PCT/US12/30084, supra.

Referring now to the powering circuitry 2010 in FIG. 20, advantageouslyprovided is a configuration that automatically adapts to the poweringsituation presented to the thermostat 2000 at the time of installationand thereafter in a manner that has been found to provide a goodcombination of robustness, adaptability, and foolproofness. The poweringcircuitry 2010 comprises a full-wave bridge rectifier 2020, a storageand waveform-smoothing bridge output capacitor 2022 (which can be, forexample, on the order of 30 microfarads), a buck regulator circuit 2024,a power-and-battery (PAB) regulation circuit 9528, and a rechargeablelithium-ion battery 2030. In conjunction with other control circuitryincluding backplate power management circuitry 2027, head unit powermanagement circuitry 2029, and the microcontroller 2008, the poweringcircuitry 2010 is configured and adapted to have the characteristics andfunctionality described hereinbelow. Description of further details ofthe powering circuitry 2010 and associated components can be foundelsewhere in the instant disclosure and/or in the commonly assigned U.S.Ser. No. 13/034,678, supra, and U.S. Ser. No. 13/267,871, supra.

By virtue of the configuration illustrated in FIG. 20, when there is a“C” wire presented upon installation, the powering circuitry 2010operates as a relatively high-powered, rechargeable-battery-assistedAC-to-DC converting power supply. When there is not a “C” wirepresented, the powering circuitry 2010 operates as a power-stealing,rechargeable-battery-assisted AC-to-DC converting power supply. Asillustrated in FIG. 20, the powering circuitry 2010 generally serves toprovide the voltage Vcc MAIN that is used by the various electricalcomponents of the thermostat 2000, and that in one embodiment willusually be about 4.0 volts. As used herein, “thermostat electrical powerload” refers to the power that is being consumed by the variouselectrical components of the thermostat 2000. Thus, the general purposeof powering circuitry 2010 is to judiciously convert the 24VAC presentedbetween the input leads 2019 and 2017 to a steady 4.0 VDC output at theVcc MAIN node to supply the thermostat electrical power load. Detailsrelating to bootstrap circuitry (not shown), whose purpose is to providea kind of cruder, less well-regulated, lower-level electrical power thatassists in device start-up and that can act as a kind of short termsafety net, are omitted from the present discussion for purposes ofclarity of description, although further information on such circuitrycan be found in U.S. U.S. Ser. No. 13/034,678, supra.

Operation of the powering circuitry 2010 for the case in which the “C”wire is present is now described. Although the powering circuitry 2010may be referenced as a “power-stealing” circuit in the general sense ofthe term, the mode of operation for the case in which the “C” wire ispresent does not constitute “power stealing” per se, because there is nopower being “stolen” from a wire that leads to an HVAC call relay coil(or to the electronic equivalent of an HVAC call relay coil for somenewer HVAC systems). For the case in which the “C” wire is present,there is no need to worry about accidentally tripping (for inactivepower stealing) or untripping (for active power stealing) an HVAC callrelay, and therefore relatively large amounts of power can be assumed tobe available from the input at nodes 2019/2017. When the 24VAC inputvoltage between nodes 2019 and 2017 is rectified by the full-wave bridgerectifier 2020, a DC voltage at node 2023 is present across the bridgeoutput capacitor 2022, and this DC voltage is converted by the buckregulator 2024 to a relatively steady voltage, such as 4.45 volts, atnode 2025, which provides an input current I_(BP) to thepower-and-battery (PAB) regulation circuit 2028.

The microcontroller 2008 controls the operation of the poweringcircuitry 2010 at least by virtue of control leads leading between themicrocontroller 2008 and the PAB regulation circuit 2028, which for oneembodiment can include an LTC4085-3 chip available from LinearTechnologies Corporation. The LTC4085-3 is a USB power manager andLi-Ion/Polymer battery charger originally designed for portablebattery-powered applications. The PAB regulation circuit 2028 providesthe ability for the microcontroller 2008 to specify a maximum valueI_(BP)(max) for the input current I_(BP). The PAB regulation circuit2028 is configured to keep the input current at or below I_(BP)(max),while also providing a steady output voltage Vcc, such as 4.0 volts,while also providing an output current Icc that is sufficient to satisfythe thermostat electrical power load, while also tending to the chargingof the rechargeable battery 2030 as needed when excess power isavailable, and while also tending to the proper discharging of therechargeable battery 2030 as needed when additional power (beyond whatcan be provided at the maximum input current I_(BP)(max)) is needed tosatisfy the thermostat electrical power load. If it is assumed for thesake of clarity of explanation that the voltages at the respectiveinput, output, and battery nodes of the PAB regulation circuit 2028 areroughly equal, the functional operation of the PAB regulation circuit2028 can be summarized by relationship I_(BP)=Icc+I_(BAT), where it isthe function of the PAB regulation circuit 2028 to ensure that I_(BP)remains below I_(BP)(max) at all times, while providing the necessaryload current Icc at the required output voltage Vcc even for cases inwhich Icc is greater than I_(BP)(max). The PAB regulation circuit 2028is configured to achieve this goal by regulating the value of I_(BAT) tocharge the rechargeable battery 2030 (I_(BAT)>0) when such charge isneeded and when Icc is less than I_(BP)(max), and by regulating thevalue of I_(BAT) to discharge the rechargeable battery 2030 (I_(BAT)<0)when Icc is greater than I_(BP)(max).

For one embodiment, for the case in which the “C” wire is present, thevalue of I_(BP)(max) for the PAB regulation circuit 2028 is set to arelatively high current value, such as 100 mA, by the microcontroller2008. Assuming a voltage of about 4.45 volts at node 2025, thiscorresponds to a maximum output power from the buck regulator 2024 ofabout 445 mW. Advantageously, by virtue of the rechargeablebattery-assisted operation described above, the powering circuitry 2010can provide instantaneous thermostat electrical power load levels higherthan 445 mW on an as-needed basis by discharging the rechargeablebattery, and then can recharge the rechargeable battery once theinstantaneous thermostat electrical power load goes back down. Generallyspeaking, depending especially on the instantaneous power usage of thelarge visually pleasing electronic display (when activated by the usercoming close or manipulating the user interface), the high-poweredmicroprocessor 2032 (when not in sleep mode), and the Wi-Fi chip (whentransmitting), the instantaneous thermostat electrical power load canindeed rise above 445 mW by up to several hundred additional milliwatts.For preferred embodiments in which the rechargeable battery 2030 has acapacity in the several hundreds of milliamp-hours (mAh) at or near thenominal Vcc voltage levels (e.g., 560 mAh at 3.7 volts), supplying thisamount of power is generally not problematic, even for extended timeperiods (even perhaps up to an hour or more), provided only that thereare sufficient periods of lower-power usage below 445 mW in which therechargeable battery 2030 can be recharged. The thermostat 2000 isconfigured such that this is easily the case, and indeed is designedsuch that the average power consumption is below a much lower thresholdpower than this, as discussed further below in the context of “activepower stealing.”

Operation of the powering circuitry 2010 for the case in which the “C”wire is not present is now described. For such case, in accordance withthe above-described operation of insertion sensing components/switches2012/2016, it will be the Y-lead that is connected to the node 2019 if a“Y” wire has been inserted, and it will otherwise be the W-lead that isconnected to the node 2019 if no “Y” wire has been inserted. Stateddifferently, it will be the Y-lead from which “power is stolen” if a “Y”wire has been inserted, and it will otherwise be the W-lead from which“power is stolen” if no “Y” wire has been inserted. As used herein,“inactive power stealing” refers to the power stealing that is performedduring periods in which there is no active call in place based on thelead from which power is being stolen. Thus, for cases where it is the“Y” lead from which power is stolen, “inactive power stealing” refers tothe power stealing that is performed when there is no active coolingcall in place. As used herein, “active power stealing” refers to thepower stealing that is performed during periods in which there is anactive call in place based on the lead from which power is being stolen.Thus, for cases where it is the “Y” lead from which power is stolen,“active power stealing” refers to the power stealing that is performedwhen there is an active cooling call in place.

Operation of the powering circuitry 2010 for “inactive power stealing”is now described. In the description that follows it will be assumedthat the “Y” wire has been inserted and therefore that power is to bestolen from the Y-lead, with it being understood that similarcounterpart operation based on the “W” lead applies if no “Y” wire hasbeen inserted and power is to be stolen from the W-lead. During inactivepower stealing, power is stolen from between the “Y” wire that appearsat node 2019 and the Rc lead that appears at node 2017. As discussedpreviously, the Rc lead will be automatically shorted to the Rh lead (toform a single “R” lead) for a single-HVAC transformer system, while theRc lead will be automatically segregated from the Rh lead for adual-HVAC transformer system. In either case, there will be a 24VAC HVACtransformer voltage present across nodes 2019/2017 when no cooling callis in place (i.e., when the Y-Rc FET switch is open). For oneembodiment, the maximum current I_(BP)(max) is set to a relativelymodest value, such as 20 mA, for the case of inactive power stealing.Assuming a voltage of about 4.45 volts at node 2025, this corresponds toa maximum output power from the buck regulator 2024 of about 90 mW. Thepower level of 90 mW has been found to be a generally “safe” powerstealing level for inactive power stealing, where the term “safe” isused to indicate that, at such power level, all or virtually all HVACcooling call relays that are installed in most residential andcommercial HVAC systems will not accidentally trip into an “on” statedue to the current following through the cooling call relay coil. Duringthis time period, the PAB regulator 2028 operates to discharge thebattery 2030 during any periods of operation in which the instantaneousthermostat electrical power load rises above 90 mW, and to recharge thebattery (if needed) when the instantaneous thermostat electrical powerload drops below 90 mW. Provided that the rechargeable battery 2030 isselected to have sufficient capacity (such as 560 mAh at 3.7 volts asdiscussed above), supplying power at above 90 mW (even several hundredmilliwatts more) is generally not problematic even for extended timeperiods (even perhaps up to an hour or more), provided only that thereare sufficient periods of lower-power usage below 90 mW in which therechargeable battery 2030 can be recharged. The thermostat 2000 isconfigured such that the average power consumption is well below 90 mW,and indeed for some embodiments is even below 10 mW on a long term timeaverage.

According to one embodiment, the powering circuitry 2010 is furthermonitored and controlled during inactive power stealing by themicrocontroller 2008 by virtue of monitoring the voltage V_(BR) acrossthe bridge output capacitor 2022 at node 2023 that leads into the buckregulator 2024. For the embodiment of FIG. 20, the voltage VBR ismonitored directly by virtue of an analog to digital converter (“ADC”)that is built into the microcontroller 2008. According to an embodiment,the voltage V_(BR) across the bridge output capacitor 2022 can bemonitored, either on a one-time basis, a periodic basis, or a continuousbasis to assess a general “strength” of the HVAC system with respect tothe power that can be safely provided during inactive power stealing.This assessment can then be used to adjust a determination for themaximum “safe” amount of power that can be provided at the output ofbuck regulator 2024 during inactive power stealing, which can in turn beimplemented by the microcontroller 2008 by setting the maximum inputcurrent I_(BP)(max) of the PAB regulator 2028 for inactive powerstealing. In one particularly advantageous embodiment, at the outset ofan inactive power stealing period (either on a one-time basis afterthermostat installation or on ongoing basis as desired), themicrocontroller 2008 initially sets the maximum current I_(BP)(max) tozero and measures the resultant voltage V_(BR). This “open-circuit”value of V_(BR) will typically be, for example, somewhere around 30volts. The microcontroller 2008 then sets the maximum currentI_(BP)(max) to 20 mA and measures the resultant voltage V_(BR). If thevalue of V_(BR) when I_(BP)(max)=20 mA remains roughly the same as itsopen-circuit value (less than a predetermined threshold difference, forexample), then it is determined that the HVAC system is “strong enough”at the Y-lead to accommodate a higher value for the maximum currentI_(Bp)(max), and the microcontroller 2008 increases the maximum currentI_(BP)(max) to 40 mA (corresponding to a maximum “safe” power stealinglevel of about 180 mW assuming 4.45 volts). On the other hand, if thevalue of V_(BR) when I_(BP)(max)=20 mA tends to sag relative to itsopen-circuit value (greater than the predetermined threshold difference,for example), then it is determined that the HVAC system is not “strongenough” at the Y-lead to accommodate an increased maximum currentI_(BP)(max), and its value will remain fixed at 20 mA. Optionally, thisprocess can be repeated to further increase the maximum currentI_(BP)(max) to successively higher levels, although care should be takento ensure by empirical testing with a target population of HVAC systemsthat the cooling call relay will not be tripped at such higher levelsduring inactive power stealing. For one embodiment, the process stopswhen I_(BP)(max)=40 mA, to avoid accidental cooling call relay trippingacross a very large population of HVAC systems.

Operation of the powering circuitry 2010 for “active power stealing” isnow described. In the description that follows it will be assumed thatthe “Y” wire has been inserted and therefore that power is to be stolenfrom the Y-lead, with it being understood that similar counterpartoperation based on the “W” lead applies if no “Y” wire has beeninserted. During an active cooling call, it is necessary for current tobe flowing through the HVAC cooling call relay coil sufficient tomaintain the HVAC cooling call relay in a “tripped” or ON state at alltimes during the active cooling call. In the absence of power stealing,this would of course be achieved by keeping the Y-Rc FET switch 2006 inON state at all times to short the Y and Rc leads together. To achieveactive power stealing, the microcontroller 2008 is configured by virtueof circuitry denoted “PS MOD” to turn the Y-Rc FET switch OFF for smallperiods of time during the active cooling call, wherein the periods oftime are small enough such that the cooling call relay does not“un-trip” into an OFF state, but wherein the periods of time are longenough to allow inrush of current into the bridge rectifier 2020 to keepthe bridge output capacitor 2022 to a reasonably acceptable operatinglevel. For one embodiment, this is achieved in a closed-loop fashion inwhich the microcontroller 2008 monitors the voltage V_(BR) at node 2023and actuates the signal Y-CTL as necessary to keep the bridge outputcapacitor 2022 charged. By way of example, during active power stealingoperation, the microcontroller 2008 will maintain the Y-Rc FET switch inan ON state while monitoring the voltage V_(BR) until it drops below acertain lower threshold, such as 8 volts. At this point in time, themicrocontroller 2008 will switch the Y-Rc FET switch into an OFF stateand maintain that OFF state while monitoring the voltage V_(BR), whichwill rise as an inrush of rectified current charges the bridge capacitor2022. Then once the voltage V_(BR) rises above a certain upperthreshold, such as 10 volts, the microcontroller 2008 will turn the Y-RcFET switch back into in an ON state, and the process continuesthroughout the active power stealing cycling. Although the scope of thepresent teachings is not so limited, the microcontroller 2008 ispreferably programmed to keep the maximum current I_(BP)(max) to arelatively modest level, such as 20 mA (corresponding to a maximum“safe” power stealing level of about 90 mW assuming 4.45 volts)throughout the active power stealing cycle. The circuit elements aredesigned and configured such that the ON-OFF cycling of the Y-Rc FETswitch occurs at a rate that is much higher than 60 Hz and generally hasno phase relationship with the HVAC power transformer, whereby thespecter of problems that might otherwise occur due to zero crossings ofthe 24VAC voltage signal are avoided. By way of example and not by wayof limitation, for some embodiments the time interval required forcharging the bridge output capacitor 2022 from the lower threshold of 8volts to the upper threshold of 10 volts will be on the order 10 to 100microseconds, while the time that it takes the bridge output capacitor2022 to drain back down to the lower threshold of 8 volts will be on theorder of 1 to 10 milliseconds. It has been found that, advantageously,at these kinds of rates and durations for the intermittent “OFF” stateof the Y-Rc FET switch 2006, there are very few issues brought about byaccidental “un-tripping” of the HVAC cooling call relay during activepower stealing across a wide population of residential and commercialHVAC installations.

According to one embodiment, it has been found advantageous to introducea delay period, such as 60-90 seconds, following the instantiation of anactive cooling cycle before instantiating the active power stealingprocess. This delay period has been found useful in allowing manyreal-world HVAC systems to reach a kind of “quiescent” operating statein which they will be much less likely to accidentally un-trip away fromthe active cooling cycle due to active power stealing operation of thethermostat 2000. According to another embodiment, it has been foundfurther advantageous to introduce another delay period, such as 60-90seconds, following the termination of an active cooling cycle beforeinstantiating the inactive power stealing process. This delay period haslikewise been found useful in allowing the various HVAC systems to reacha quiescent state in which accidental tripping back into an activecooling cycle is avoided. Preferably, the microcontroller 2008implements the above-described instantiation delays for both active andinactive power stealing by setting the maximum current I_(BP)(max) tozero for the required delay period. In some embodiments, the operationof the buck regulator circuit 2024 is also shut down for approximatelythe first 10 seconds of the delay period to help ensure that the amountof current being drawn by the powering circuitry 2010 is very small.Advantageously, the rechargeable-battery-assisted architecture of thepowering circuitry 2010 readily accommodates the above-describedinstantiation delays in that all of the required thermostat electricalpower load can be supplied by the rechargeable battery 2030 during eachof the delay periods.

FIG. 21 shows an illustrative thermostat 2100 according to an embodimentoperative to take advantage of various HVAC wiring configurations, ifavailable, to maximize power consumption efficiency. Thermostat 2100includes many of the same components and configuration as thermostat2000 of FIG. 20. For ease of discussion, elements referred to inconnection with FIG. 21 having the same two least significant digits(the two x's in 21xx) are essentially the same as the elements havingthe same two least significant digits referred to in connection withFIG. 20. Compared to thermostat 2000, thermostat 2100 replaces block2016 with power wire selection circuitry 2140 and adds control line2150, which connects circuitry 2140 with microcontroller 2108. Doublelines 2015 termed “mechanical causation” are shown removed, but mayoptionally be included as part of thermostat 2100. It is understood thatalthough FIG. 21 and its accompanying discussion elements are notincluded in FIG. 20, the functionality of thermostat 2100 can beimplemented by thermostat 2000.

Power wire selection circuitry 2140 can include input nodes 2141-2144,control node 2145, power node 2146, and switch electronics 2147. Powernode 2146 is connected to switch circuitry 2147 and to full-wave bridgerectifier 2120. Control node 2145 is connected to switch circuitry 2147and microcontroller 2108. Input nodes 2141-2144 are connected to switchcircuitry 2147 and are electrically coupled to different wiringconnectors 2114. In particular, node 2141 is connected to the commonwire connector, node 2142 is connected to the W call relay connector,node 2143 is connected to the Y call relay connector, and node 2144 isconnected to the G call relay wire. Although FIG. 21 shows selectioncircuitry 2140 having four input nodes, it is understood that any numberof input nodes may be included. In addition, the input nodes can beconnected to any of wiring connectors 2114, except for return relaypower wire connectors (e.g., Rc and Rh connectors). In one embodiment,selection circuitry 2140 can include an input node for each call relayconnector (e.g., a node for the W, Y, O/B, G, and AUX call relayconnectors), and an input node for the common wire connector. In anotherembodiment, selection circuitry 2140 can include fewer nodes thanavailable call relay wiring connectors, but no node for a common wireconnector. In yet another embodiment, selection circuitry 2140 caninclude a node for a common wire connector and one or two call relayconnectors.

Power wire selection circuitry 2140 is operative to selectively connectpower node 2146 to one of input nodes 2141-2144 based on a signalreceived at control node 2145. Switch circuitry 2147 can includecircuitry (e.g., FET switches) necessary to connect any one of inputnodes 2141-2144 to power node 2146. In addition, switch circuitry 2147can dynamically switch connection of power node 2146 from one input nodeto another in response to signals received at control node 2145. Forexample, microcontroller 2108 may initially instruct selection circuitry2140 to connect power node 2146 to input node 2143, and then at a latertime period, microcontroller 2108 can instruct selection circuitry 2140to connect power node 2146 to input node 2144. Determination of whichinput node is selectively coupled to power node 2146 is based, in part,on an HVAC wiring scheme, discussed below.

Thermostat 2100 is operable to function regardless of which HVAC wiringscheme is connected to wiring connectors 2114. HVAC wiring schemes caninclude three general classes of schemes: a single circuit system withno common wire, a multiple circuit system with no common wire, and acommon wire system. A single circuit system with no common wire includeswiring configurations in which only one call relay wire (e.g., W, Y, G,O/B, or AUX) and its associated return relay power wire (e.g., Rh or Rc)are connected to wiring connectors 2114, and no “C” power wire (e.g.,common wire) is connected to wiring connectors 2114. The “single”designation implies that only one call can be made by thermostat 2100for this particular HVAC wiring scheme. A specific example of a singlecircuit system is when a W (heating) call relay wire, a Rh (heat callrelay power wire), and no other HVAC wires are connected to wiringconnectors 2114. Such a circuit permits thermostat 2100 to make aheating call, but no other calls. Another specific example of a singlecircuit system is when a Y (cooling) call relay wire, a Rc (cool callrelay power wire), and no other HVAC wires are connected to wiringconnectors 2114. Such a circuit permits thermostat 2100 to make acooling call, but no other calls.

A multiple circuit system with no common wire includes wiringconfigurations in which at least two different call relay wires (e.g.,W, Y, G, O/B, or AUX) are connected to wiring connectors 2114, but no“C” power wire is connected. Connections of Rh and Rc depend on whichcall relay wires are connected, and has no bearing on whether the HVACwiring scheme is a multiple circuit system. The “multiple” designationimplies that thermostat 2100 can call at least two different calls. Aspecific example of a multiple circuit system is when the W and Y callrelay wires, but no common wire, are connected to wiring connectors2114. Another example of a multiple circuit system is when the Y and Gcall relay wires, but no common wire, are connected to the wiringconnectors 2114. Yet another example is when the W, Y, and G call relaywires, but no common wire, are connected to wiring connectors 2114.

A common wire system includes a wiring configuration in which a “C”common power wire and any combination of call relay and relay powerwires are connected to wiring connectors 2114. For example, a commonwire system can exist when the C common wire, W call relay wire, and Rhrelay power wire are connected to wiring connectors 2114.

FIG. 22 shows a flowchart 2200 showing illustrative steps for operatingan HVAC system using a thermostat in accordance with an embodiment. Thethermostat used to control the HVAC system can be, for example,thermostat 2100 of FIG. 21. Reference will be made to thermostat 2100(of FIG. 21), FIGS. 23, 24A, 24B, and 25 in connection with thediscussion corresponding to FIG. 22. Beginning with step 2210, adetermination is made as to which one of a plurality of different HVACwiring schemes is associated with the thermostat. The HVAC wiringschemes can include a single circuit system having no common wire, amultiple circuit system having no common wire, or a common wire system.Microprocessor 2108 can determine which HVAC wiring scheme is connectedto the thermostat by analyzing electrical signals 2113, which aretransmitted from insertion sensing components 2112.

At step 2220, a power scheme is implemented based on the determined HVACwiring scheme. If at, step 2230, the determined HVAC wiring scheme isthe single circuit system, the thermostat can implement a power schemethat uses active and inactive power stealing on the single circuitsystem, as indicated by step 2232. In addition, at step 2234, power wireselection circuitry is instructed to select which wiring connector isconnected to the power node. In particular, it selects an input nodeassociated with the call relay wire connected to the wiring connector ofthe single circuit system.

Referring briefly to FIG. 23, which shows a simplified illustrativeschematic of portions of thermostat 2100 wired to a single circuitsystem, the HVAC wiring scheme is a single circuit system with no commonwire because only the W heat call relay wire and the Rh heat call relaypower wire are connected to wiring connectors 2114. Thus, only the W andRh wiring connectors have HVAC wires connected to them. All other wiringconnectors are not connected to any HVAC wires. Insertion sensingcomponents 2112 can provide microcontroller 2108 with electricalinsertion sensing signals 2113 so that microcontroller 2108 candetermine that thermostat 2100 is in fact connected to a single circuitHVAC system with no common wire.

Upon making the HVAC wiring scheme determination, microcontroller 2108can instruct power wire selection circuitry 2140 to connect power node2146 to the W wiring connector. The line contained within switchcircuitry 2147 that connects the W input node 2142 to power node 2146illustrates the result of this instruction. In addition, based on thedetermined HVAC wiring scheme, microcontroller 2108 is operative toenable a power scheme that uses active and inactive power stealing.Active and inactive power stealing have been discussed above inconnection with the description accompanying FIG. 20. However, tobriefly recapitulate the above discussion, active power stealing canrefer to the process of momentarily opening a closed contact or switchduring an enabled phase of a call (e.g., a heating call), where thecontact is closed during a majority of each duty cycle when in theenabled phase. Thus, for example, during an active heating call, switch2160 is closed to form a short-circuit between the W connector and theRh connector. It is switch 2160 is that is temporarily opened duringeach duty cycle to enable power to be drawn from the W heat call relaywire even when it is in an enabled state (or short-circuited or activestate). Power is drawn from the active W heat call relay wire in amanner that does not untrip the active HVAC relay circuit. In contrast,inactive power stealing enables power to be received from an inactiveHVAC relay circuit in a manner that does not trip the inactive HVACrelay circuit. Thus, in FIG. 23, when switch 2160 is open, no shortcircuit exists between the W and Rh wiring connectors and power isstolen from the W heat call relay wire.

Referring now back to FIG. 22, if, at step 2230, the determined HVACwiring scheme is not a single circuit system, the process proceeds tostep 2240. If, at step 2240, the determined HVAC wiring scheme is amultiple circuit system with no common wire, the thermostat canimplement a power scheme that only uses inactive power stealing on anon-enabled circuit (e.g., a non-shorted circuit) within the multiplecircuit system, as indicated by step 2242. A thermostat operatingaccording to a power scheme that only uses inactive power stealing, asopposed to one that also uses active power stealing, enables thethermostat to maximize its operational power margin in a multiplecircuit system. That is, in a multiple circuit system, the thermostatcould use a power scheme that uses both inactive and active powerstealing, but an operational power savings is realized if active powerstealing is avoided. In addition, at step 2244, power wire selectioncircuitry is instructed to couple a power node to any one of the wiringconnectors associated with the multiple circuit system by selecting theappropriate input node associated with the desired wiring connector.

After the power node is initially connected to one of the wiringconnectors, the current and future states of the thermostat aremonitored to determine which, if any, HVAC circuits are changing orabout to change from an enabled state to an non-enabled state, or viceversa, as indicated by step 2246. For example, the microcontroller canbe aware of which circuits are active or enabled. In addition, themicrocontroller can also be aware of which wiring connector is connectedto the power node by virtue of controlling which input node is connectedto the power node. At step 2247, a determination is made whether thepower node is connected to a wiring connector that is changing or aboutto change its state. If YES, then at step 2248, power wire selectioncircuitry 2140 is instructed to couple the power node to a wireconnector associated with one of the HVAC circuits that is not enabledor active. After step 2248, the process loops back to step 2246 andrepeats. If the determination at step 2247 is NO, then no steps aretaken and the process loops back to step 2246 and repeats.

Referring now briefly to FIGS. 24A and 24B, which show simplifiedillustrative schematics of portions of thermostat 2100 wired to amultiple circuit system, the HVAC wiring scheme is a multiple circuitsystem with no common wire because the W heat call relay wire, Y coolingcall relay wire, the G fan call relay wire, the Rh heat call relay powerwire, and the Rc cool call relay power wire are all connected to wiringconnectors 2114. No common wire is connected to the wiring connector.For purposes of this example, the other wiring connectors may or may notbe connected to any HVAC wires. Insertion sensing components 2112 canprovide microcontroller 2108 with electrical insertion sensing signals2113 so that microcontroller 2108 can determine that thermostat 2100 isin fact connected to a multiple circuit HVAC system with no common wire.

Upon making the HVAC wiring scheme determination, microcontroller 2108can instruct power wire selection circuitry 2140 to connect power node2146 to the W wiring connector, the Y wiring connector, or the G wiringconnector by causing switch circuitry 2147 to select the appropriateinput nodes (e.g., nodes 2142-2144). In addition, the determination thatthe HVAC wiring scheme is a multiple circuit system enables thethermostat to enable a power scheme that uses only inactive powerstealing. Referring now specifically to FIG. 24A, input node 2143 iscoupled to power node 2146. Thus, power node 2146 is coupled to the Ywiring connector. In addition, for the purposes of the example beingdiscussed in connection with FIG. 24A, assume that switches 2160, 2162,and 2164 are all OFF so that none of the HVAC circuits in the system areenabled. Thus, in the configuration shown in FIG. 24A, microcontroller2108 is operative to enable inactive power stealing from the Y cool callrelay wire connected to the Y wiring connector. Moreover, because noneof the circuits are active, power node 2146 could have been coupled tonode 2142 or 2144 in the first instance.

FIG. 24B illustrates how the power node is changed from one input nodeto another in response to a changed condition in one of the HVACcircuits. Assume, now, that a cooling call is requested. In response tothis request, microcontroller 2108 causes switch 2162 to turn ON,thereby short-circuiting the Y connector with the Rc connector. Onceswitch 2162 is ON, the Y call cool relay circuit is active or enabled.Also in response to the cooling call request, microcontroller 2108 caninstruct switch circuitry 2147 to connect power node 2146 to anon-enabled HVAC circuit. Since the Y connector is now part of an activeHVAC circuit, power wire selection circuitry 2140 has to switch powernode 2146 from that connector in order to adhere to the multiple circuitsystem power scheme that uses only inactive power stealing. In thisexample, power node 2146 can be connected to the W connector via node2142 (as shown by the solid line) or to the G connector via node 2144(as indicated by the optional dashed line).

The timing of when power wire selection circuitry 2140 switches from oneinput node to another in response to knowledge that the currentlyselected input node is or is about to be associated with an enabled HVACcircuit is important to ensure inactive power stealing is the only powerstealing method used in connection with the multiple circuit system. Atany given time, the thermostat knows which HVAC circuits are enabled andwhich input node is coupled to the power node. The thermostat also knowswhen there will be changes in the status of the HVAC circuit (e.g.,whether a particular HVAC circuit will switch from an enabled state to anon-enabled state and vice versa). Having knowledge of such status, thethermostat can time the selection of the input node with the change instate of an HVAC circuit to ensure compliance with the inactive powerstealing scheme. For example, if it is known that the selected inputnode is connected to the Y wiring connector and a Y cooling call isabout to be requested, microcontroller 2108 can cause switch circuitry2147 to switch to another node (e.g., node 2142) before it turns switch21620N or it can cause switch circuitry 2147 to switch to another nodeconsistent with the activation of switch 2162.

Referring now back to FIG. 22, if, at step 2240, the determined HVACwiring scheme is not a multiple circuit system, the process proceeds tostep 2250. If, at step 2250, the determined HVAC wiring scheme is acommon wire system, the thermostat can implement a power scheme thatuses neither active power stealing nor inactive power stealing, asindicated by step 2252. In addition, at step 2254, the power wireselection circuitry is instructed to connect the power node to the Cwiring connector by selecting the input node associated with that wiringconnector.

FIG. 25 shows a simplified illustrative schematic of portions ofthermostat 2100 wired to a common wire system. The HVAC wiring scheme isa common wire system because a C wire is connected to the C wiringconnector. Whether other wires are connected to one or more other wiringconnectors does not change the status of HVAC wiring scheme. Forexample, even though the W and Rh wiring connectors have wires connectedthereto, the HVAC wiring scheme remains the same. Even if optional wires(shown as dashed lines) are connected to the Y and Rc wiring connectors,the HVAC wiring scheme is still that of a common wire system. Upondetection of this scheme, microcontroller 2108 instructs power wireselection circuitry 2140 to select input node 2141 to couple the Cwiring connector to power node 2146. Thus, the power circuitry receivesits power from the C wire connector and from no other wiring connector.

Referring back to FIG. 22, it is understood that the steps shown aremerely illustrative and that additional steps may be added, the orderingof steps may be changed, and steps may be omitted. For example, the stepof selecting which input node is connected to the power node can beperformed before executing a particular power scheme.

Whereas many alterations and modifications of the present invention willno doubt become apparent to a person of ordinary skill in the art afterhaving read the foregoing description, it is to be understood that theparticular embodiments shown and described by way of illustration are inno way intended to be considered limiting. By way of example, it iswithin the scope of the present teachings for one or more of the aboveteachings to be advantageously combined with one or more featuresdescribed in one or more of the following patent applications, each ofwhich is incorporated by reference herein: U.S. Ser. No. 13/267,871filed Oct. 6, 2011; U.S. Ser. No. 13/467,029 filed May 8, 2012; U.S.Ser. No. 13/624,878 filed Sep. 21, 2012; and U.S. Ser. No. 13/632,148filed Sep. 30, 2012. Therefore, reference to the details of thepreferred embodiments is not intended to limit their scope.

What is claimed is:
 1. A method for controlling a HVAC (heating,ventilation, and air conditioning) system, the method implemented in athermostat, the method comprising: determining one of a plurality ofdifferent HVAC wiring schemes for the thermostat, the HVAC wiringschemes comprising a single circuit system having no common wire, amultiple circuit system having no common wire, or a common wire system;and implementing a power scheme based on the determined HVAC wiringscheme, wherein: if the determined HVAC wiring scheme is the singlecircuit system, the power scheme uses active and inactive power stealingon the single circuit system; if the determined HVAC wiring scheme isthe multiple circuit system, the power scheme only uses inactive powerstealing on a non-enabled circuit within the multiple circuit system; orif the determined HVAC wiring scheme is the common wire system, thepower scheme uses neither active power stealing nor inactive powerstealing.
 2. The method according to claim 1, wherein active powerstealing comprises momentarily opening a closed contact during anenabled phase of the single circuit system.
 3. The method according toclaim 2, wherein the contact is closed during a majority of each dutycycle when the single circuit system is in the enabled phase.
 4. Themethod according to claim 1, wherein active power stealing comprisesreceiving power from an enabled HVAC relay circuit in a manner that doesnot untrip the enabled HVAC relay circuit.
 5. The method according toclaim 1, wherein inactive power stealing comprises receiving power froma non-enabled HVAC relay circuit in a manner that does not trip thenon-enabled HVAC relay circuit.
 6. The method according to claim 1,wherein the thermostat comprises a plurality of HVAC wire connectorsoperative to receive a plurality of HVAC wires corresponding to the HVACsystem and power wire selection circuitry operative to select which wireconnector is electrically coupled to a power node, the method furthercomprising: instructing the power wire selection circuitry toelectrically couple the power node to one of the HVAC wire connectorsdepending on the determined HVAC wiring scheme.
 7. The method accordingto claim 6, wherein when the determined HVAC wiring scheme is themultiple circuit system, the method further comprising: determiningwhich, if any, circuits are changing or about to change from an enabledstate to a non-enabled state or from a non-enabled state to an enabledstate; and instructing the power wire selection circuitry toelectrically couple the power node to a HVAC wire connector associatedwith one of the circuits that is in the non-enabled state.
 8. The methodaccording to claim 6, wherein when the determined HVAC wiring scheme isthe multiple circuit system, the multiple circuit system including firstand second switch circuits, the method further comprising: at a firsttime period, the first and second switch circuits are in a non-enabledstate; instructing the power wire selection circuitry to electricallycouple the power node to the HVAC wire connector associated with thefirst switch circuit during the first time period; at a second timeperiod, the first switch circuit switches from the non-enabled state toan enabled phase and that the second switch circuit is in thenon-enabled state; and instructing the power wire selection circuitry toelectrically couple the power node to the HVAC wire connector associatedwith the second switch circuit during the second time period.
 9. Athermostat, comprising: a plurality of HVAC (heating, ventilation, andair conditioning) wire connectors operative to receive a plurality ofHVAC wires corresponding to an HVAC system; control circuitry operativeto at least partially control the operation of the HVAC system; powerwire selection circuitry connected to the HVAC wire connectors and tothe control circuitry, the power wire selection circuitry operative toselect which wire connector is electrically coupled to a power node;powering circuitry operative to receive power from the power wireselection circuitry via the power wire selection circuitry; wherein thecontrol circuitry is further operative to: determine an HVAC wiringscheme based on which wire connectors have received HVAC wires; causethe power circuitry to operate according to a selected one of aplurality of power schemes based on the determined HVAC wiring scheme;and instruct the power wire selection circuitry to selectively couple apredetermined one of the wire connectors to the power node based on thedetermined HVAC wiring scheme and the selected power scheme.
 10. Thethermostat according to claim 9, wherein when the HVAC wiring scheme isindicative of a single HVAC circuit having a wire connector connected toa HVAC call relay coil and no common wire is connected to any of thewire connectors, the control circuitry instructs the power wireselection circuitry to couple the wire connector associated with theHVAC call relay coil to the power node.
 11. The thermostat according toclaim 10, wherein the control circuitry further enables the powercircuitry to inactively steal power from the HVAC call relay coil whenthe single HVAC circuit is not experiencing an active HVAC call and toactively steal power from the HVAC call relay coil when the singe HVACcircuit is experiencing an active HVAC call.
 12. The thermostataccording to claim 9, wherein the HVAC wiring scheme is indicative ofmultiple HVAC circuits each having a wire connector connected to adifferent HVAC call relay coil and no common wire is connected to any ofthe wire connectors.
 13. The thermostat according to claim 12, whereinthe control circuitry is further operative to cause the power circuitryto operate according to an inactive power stealing scheme regardless ofwhether any one of the multiple HVAC circuits is experiencing an activeHVAC call.
 14. The thermostat according to claim 13, wherein the controlcircuitry is further operative to instruct the HVAC wire selectioncircuitry to selectively couple the power node to the wire connectorassociated with the HVAC call relay coil of any one of the multiple HVACcircuits that is NOT experiencing an active HVAC call.
 15. Thethermostat according to claim 13, wherein the multiple HVAC circuitscomprise first and second HVAC circuits, the first HVAC circuitcomprising a first HVAC call relay coil and the second HVAC circuitcomprising a second HVAC call relay coil.
 16. The thermostat accordingto claim 15, wherein, at a first time period, the power node isconnected to the wire connector associated with the first HVAC callrelay coil and the first and second HVAC circuits are both NOTexperiencing an active HVAC call; at a second time period after thefirst time period, the first HVAC circuit switches from NOT experiencingan active HVAC call to experiencing an active HVAC call, and the secondHVAC circuit is NOT experiencing an HVAC call; and in response to thefirst HVAC circuit switching to an active HVAC, the control circuitry isfurther operative to instruct the HVAC wire selection circuitry toselectively couple the power node to the wire connector associated withthe second HVAC call relay coil.
 17. The thermostat according to claim16, wherein the control circuitry is operative to cause the powercircuitry to inactively power steal from the first HVAC call relay coilduring the first time period.
 18. The thermostat according to claim 16,wherein the control circuitry is operative to cause the power circuitryto inactively power steal from the second HVAC call relay coil duringthe second time period.
 19. The thermostat according to claim 9, whereinwhen the HVAC wiring scheme is indicative of a common wire connected toone of the wire connectors, the control circuitry is further operativeto: instruct the HVAC wire selection circuitry to couple the power nodeto the wire connector associated with the common wire; and enable thepower circuitry to draw more power from the wire connector associatedwith the common wire than the power circuitry can draw when operatingaccording to one of the power stealing schemes.
 20. A thermostat,comprising: a plurality of wiring connectors operative to connect to aplurality of HVAC wires; insertion sensing circuitry operative toprovide insertion sensing signals indicative of which wiring connectorshave an HVAC wire connected thereto; power wire selection circuitrycomprising an output node, a control node, and at least two input nodes,each input node is electrically coupled to a different one of at leasttwo wiring connectors, the power wire selection circuitry operative toselectively couple any input node to the output node based on a signalreceived at the control node; a microcontroller operative to receive theinsertion sensing signals and process HVAC call signals, the HVAC callsignals including at least two different types of calls, themicrocontroller further operative to: determine an HVAC wiring schemebased on the received insertion sensing signals; implement a powerscheme based on the determined HVAC wiring scheme; provide a selectionsignal to the control node based on the determined HVAC wiringconfiguration, the HVAC call signal, and the implemented power scheme.21. The thermostat according to claim 20, wherein when the HVAC wiringconfiguration is indicative of a single HVAC circuit with no commonwire, the implemented power scheme includes in-active power stealing andactive power stealing.
 22. The thermostat according to claim 20, whereinwhen the HVAC wiring configuration is indicative of a single HVACcircuit with no common wire, the selection signal causes the powerselection circuitry to permanently couple the output node to the inputnode associated with the wiring connector associated with the relay wireof the single-circuit HVAC connection.
 23. The thermostat according toclaim 20, wherein when the HVAC wiring configuration is indicative ofmultiple HVAC circuits with no common wire, the implemented power schemeonly uses in-active power stealing.
 24. The thermostat according toclaim 20, wherein when the HVAC wiring configuration is indicative ofmultiple HVAC circuits with no common wire, and the HVAC call signalrequires use of a first of the HVAC circuits, the selection signalcauses the power selection circuitry to couple the output node to theinput node associated with the wiring connector associated with a secondof the HVAC circuits.
 25. A thermostat for use in connection with a HVAC(heating, ventilation, and air conditioning) system, the HVAC systemhaving a single circuit system, a multiple circuit system, or a commonwire system, the thermostat comprising: insertion sensing circuitryoperative to provide insertion sensing signals indicative of which HVACsystem is connected to the thermostat; and control circuitry operativeto: receive the insertion sensing signals; and engage in single circuitpower stealing, multi-circuit power stealing, or common wire powerutilization for obtaining power from the HVAC system based on thereceived insertion sensing signals.
 26. The thermostat of claim 25,wherein the multi-circuit power stealing comprises a power scheme thatonly uses inactive power stealing regardless of whether active powerstealing could be used.
 27. The thermostat of claim 25, wherein thesingle circuit power stealing comprises a power scheme that uses activepower stealing and inactive power stealing.